I learned to give head in a very incremental way; for me, it was a process of learning one small simple aspect of the whole to the point where I could do it without paying attention - acquiring a muscle-memory -- and then going on to the next. I'll explain it the same way; I encourage guys who may be reading this to be patient and encouraging with women who are learning, and women to be patient with themselves.
From the basics to the advanced moves:
1. Get it wet--
The opening move: start by getting his dick nice and wet. First work up some spit, then slide your mouth over the head of his dick and drool on it; take it out of your mouth and give it some wet sloppy mouthing up and down the full length on both sides. For style points you can do this with a head-tilt and an upward-pointed smile, but strictly speaking it's purely technical: you want that dick slick and spit-lubed for the moves to follow. During the course of the BJ, continue to drool on his dick.
2. No teeth --
It goes without saying that teeth are bad. The general wisdom is that the way to avoid this is to cover your teeth with your lips (i.e. fold your lips over your teeth completely, like you're making a granny-with-dentures-face), which isn't really viable: any one-shot cocksucker can tell you that this will prevent you from forming a seal around the dick in your mouth, and is somewhat uncomfortable to boot. What you actually want is to have your lips tensed, not unlike how you would tense them to blow a kiss: when you open your mouth, this will keep them closed in well past where your teeth begin. If you're confused about what I mean, try the following:
First, hold a pencil up in front of your face. Then, pick up the pencil with your mouth using only your lips - no teeth. Your lips should be in roughly the correct configuration, tensed and extended. Add suction to that, and they will effectively cover your teeth while giving head.
3. The basic move--
This isn't a proper blowjob on its own, but it's the foundation of a BJ. If you're just trying this for the first time, it may be easiest if you hold onto his penis at the base and rest your free hand against a steady surface such as the edge of the bed or a wall. This is how you coordinate the movement of your lips and your tongue, which is what's really important:
Lips puckered, form a seal over the very end of his penis with your tongue resting against the tip. Then, simultaneously slide the your lips and the tensed tip of your tongue forward along him until your tongue-tip is a little past the frenulum, which is the sensitive area on the underside of the dick where the shaft joins the head. Once you're past the frenulum, stop and slide your lips (and tensed tongue-tip) back until your lips are again pursed around the tip, tongue resting against it.
The trick to coordinating your tongue and your lips in this is the rhythm of it: lips forward, tongue-tip forward. lips back, tongue-tip back. The fact that everything's moving in the same direction makes it possible to do several things simultaneously. Do this until it feels totally natural and easy.
4. The basic move, redux--
Once the basic move feels easy and natural, you can turn it into a competent if not particularly flashy blowjob with the addition of just one more movement:
Instead of simply holding him at the base with your hand, close your hand around his cock just forward of where your lips rest when you start. As you slide your mouth and tongue down over the head of his cock, slide your closed fingers forward all the way to the base; as you slide your mouth and tongue back up to the tip, slide your closed fingers back up also until they are again just forward of your lips.
Just as the rhythm when coordinating your lips and tongue was lips-forward/tongue-forward, lips-back/tongue-back, the rhythm you acquire now should be mouth-forward/hand-forward, mouth-back/hand-back. You want to time this so that his dick gets as deep as it's going in your mouth at the same time your hand hits the base of his shaft, and your tongue is at the tip of his dick when your hand meets your lips. This is where it becomes important that you keep him nice and wet.
Once you can pull this off, you're competently giving head! Congratulations. :D This seems complicated, but faster than you can say "That was awesome," it'll become familiar to the point that you can add variations and pay attention to other things as well. It only gets more fun from here.
5. Functional flare: once you have the basic move redux down, the simplest and most functional way to take it up a notch is to cradle his balls as you suck and stroke. This can be a useful indication of when he's going to come, as described below:
BASIC LEVEL TRICKS AND TIPS:
* How to know when he's getting close: As your man gets closer to climax, his body will clue you in to what's coming; in most cases he'll start to ooze precum, and his balls will tighten up closer to his body. If you are cradling his balls you'll be able to feel this happen, which can be useful as a cue to adjust your speed. When he's actually going to come, it's common courtesy for him to tell you: I've never had a guy not, that I can remember. Some men, wonderful beautiful darling men, also make noises that indicate how they are reacting to what you're doing or express their verbal appreciation. Pay attention to his breath rate, and any noises he makes.
* Speed -- While timing is more of an art than a science, my experience with BJ speed runs something like this: once you have movements of the basic BJ down, going at a comfortable/natural speed is sufficient to get him most of the way to orgasm. When you sense that he's approaching, you'll want to speed up to a less comfortable pace - but you probably won't have to go fast for long. If you're totally baffled about timing, you can ask him to guide you.
* If you're just starting out, there's no need to try to go deep. The most sensitive part of the penis is the frenulum, which is where the corona (flared, fleshy edge of the head) joins the shaft on the bottom of the penis. Most of your attention (and virtually all of your tongue-focus, except anything you're doing to be visually interesting) should be focused on this spot when you're just starting out. A feeling of penetration is of secondary (but significant!) importance, but can be much more easily achieved by using your hand to stroke as you suck.
* Positioning: The most comfortable place for me to give head, personally, is on my knees on a carpeted (or blanket-draped) floor. Some women prefer to crouch over their man while he's in a prone position; do whatever is most comfortable to you. I've always kind of wanted to blow a standing man, but somehow none have been able to keep their knees locked to completion; I don't know if this is a testament to my cocksucking ability or proof positive that Hollywood sold me a lie.
* Beginner-level flare: the simplest way to add flare to the basic bj is to stimulate more of his senses; for example, moan around his dick. Men are very visually keyed: smiling up at him with his cock in your mouth (he'll be able to see the smile at the corners of your eyes and mouth) is the simplest example of this. You can also take his dick out of your mouth and rub it against your cheeks and mouth, or lick it like an ice-cream cone while you look up at him.
* Warning! Arguably the most annoying thing about giving head is having your hair get in the way and/or in your mouth. You may want to pull it back first, or have him hold it back for you. Some boys are better at this than others.
In the intermediate level, I've grouped additional hints and tricks that can make your blowjob better for everyone involved. To deal with truly recalcitrant motherfuckers who absolutely will not finish, consult the Advanced section. Some of this is actually easier than the stuff in the "Beginner" section, but I put it here on the theory that adding more frosting to a bad cake isn't really helpful to anyone at the birthday party.
1. Play with his balls while you suck --
If you're familiar with the contents of the Beginner section, you'll already be able to cradle his balls as you give head; a simple addition to this is to play with them, gently, as you suck. The usual (I think?) way to do this is to roll your fingers, like you're playing with peace balls.
2. The Wrist Twist --
The big intermediate move: as you stroke his dick while giving head, twist your wrist. You want to make this a two-part movement that synchronizes with the rest of the BJ, so you can keep your rhythm; for example, twist left on the downstroke, right on the upstroke. A little weird at first, but not actually all that difficult per se. I have talked to dudes who use this move to distinguish an expert BJ from one that is merely good.
3. The Double Wrist-Twist --
A variation on the wrist-twist, this involves using both your hands to stroke and twisting your wrists in opposite directions. (i.e. down -- right wrist twists left, left wrist twists right; up -- right wrist twists right, left wrist twists left) A dude need not be super-long for this to work; unless he's truly endowed, this will probably involve using just one or two fingers from each hand.
4. Lick his Balls --
One of the classics, right? You can gently take his balls into your mouth one at a time to suck and lick, or lick them all over; my favorite variation on this is probably to lap upward along the seam between his balls with small tensed-tongue strokes, from back to front.
5. Just behind his balls --
Just behind a man's balls, on the forward end of the space between testacles and anus, is a fun place to play with; pressure here with your fingers or pointed tongue can indirectly stimulate his prostate, so be sure to play a little. And speaking of prostate stimulation --
6. Ass play --
Ok, some people are freaked out by the very idea. This is, in any event, something I've only ever done by request - but this is how you go about it: With wet/lubed clean finger(s) with clipped nail(s), first gently tickle or massage his asshole. If the reception is good, you can try some penetration; your palm should be curved along the seam of his ass, fingers crooked toward yourself as you slide them into him. If all goes well to the second knuckle and he still seems to be into it, bend your penetrating finger further down - like you're trying to touch your palm. This will crook your finger or fingers into his prostate. Be gentle in there.
7. Go Deep --
I'll preface this: I'm not really a deepthroater. Even if you - like me - can't go all the way down all the time, though, going as deep as you can sometimes for variety can be very exciting for a guy you're going down on. Of possible help to readers, though: I've recently made some progress with the whole "going deep" thing, and so far my strides forward have involved the following:
First of all, the common wisdom is that you should "swallow" when the dick hits the back of your mouth, but this is frankly not the case. The movement involved is much closer to - at the risk of seeming unladylike - belching on cue. If you can't burp on command, the muscles I'm talking about are the lower end of the set you use when you make the noise commonly transcribed in english as "gulp."
Second, positioning is very very important. You want to be in a position where you can tilt your head back as far as possible, creating a single clean line for the dick to penetrate. Otherwise, the back of your throat is a 90 degree angle; most normally-shaped dicks simply do not bend that far.
Third, in order to get a dick past the back of your throat it helps to keep it to the far left or far right side of your mouth. That's all my findings for now; if you can go deep on every stroke, I tip my hat to you.
8. Use your tits --
If you've got the rack for it, you can hold your breasts together and use them to stroke him (or allow him to thrust between them) while you lick or suck the head of his cock.
So, between the Beginner basics, the Intermediate flare and any personal flourishes you add... Most dudes will pop like warm champagne. But in the event that that's not enough (and occasionally it's not), there are a few tricks at the bottom of the bag that you can whip out for dudes who need a blowjob that absolutely does not fuck around.
1. Finger Tunnel --
Some guys need to feel like they're thrusting into something tight - and when I say tight, I mean tight. This is a tricky feeling to create with your mouth, because your mouth is not a particularly tight orifice for cocksucking purposes (and if it were, teeth would be a serious problem). The solution to this is:
Rather than starting your fingers just forward of your lips when you suck cock, start them where your lips would ordinarily be - closed around the very tip of his penis. Keep your tongue-tip between your fingers as it would ordinarily be between your lips, and use your thumb and index finger to make a tight ring. Tight, as in smaller around than his penis. For this trick, don't try to form a seal around his dick with your mouth; when you're as far up as you get, your mouth won't even fully be on him but will rather be an extension of your hand.
As you stroke downward, allow the head of his cock to force your fingers open wider only against resistance, so it feels like he's pushing into something very snug. Stroke your tongue forward along his frenulum as you normally would and stop your mouth-movement where it would ordinarily stop, but stroke your fingers all the way to the base of his penis and then back up.
On the upstroke, tighten your fingers back around his penis as you draw back - returning you to your original position at the far end of the upstroke, with tight fingers in a ring around the very tip of his cock and tongue-tip between them. Conceptually this is simple, but actually doing it is sort of tricky and requires some coordination. For bonus points, you can try and add the wrist twist to this blowjob; I find it very hard to functionally use my other hand while doing this, because of the level of focus required.
You want much less resistance on the upstroke than on the downstroke; the primary focus point should be on the downstroke, when your fingers should be almost too tight for the head of his dick to fully penetrate.
2. Old Lady Mouth --
This is another trick for guys who are exceptionally hard to get off, and require a much higher level of stimulation than the average dude. Instead of creating a seal with soft lips when you put your mouth on his dick:
First, lick your lips to thoroughly moisten them. Then fold them down over your teeth - as you would if you were imitating a granny with dentures. This will create a ridge of teeth softened by the lip that's over them; on the downstroke, drag this ridge over the frenulum and (to a lesser extent) the mirroring ridge on top over the top of his cockhead. Otherwise, blow as normal.
This is less technically difficult than the finger tunnel, but comes with its own pitfalls: primarily, that it's easy to give yourself what amounts to a fat lip this way. After 3-4 minutes of this - and I generally only do this for occasional variety or on boys who are guaranteed to take more than 3-4 minutes - it can become pretty uncomfortable. Just think, though: you never remember the pain later! Also, if you're like me, the metal-taste on the inside of your lips for 48 hours later is more of a bonus than a loss.
Once you have both mastered, you can use this with the finger tunnel for an extremely high-impact BJ; this is too intense for some guys, though, since it amounts to borderline rough handling.