How do I go about giving a blow job?

Its amazing how many times this question has appeared. You could scroll back through the questions and check out the answers, but here is my answer:
Don't be afraid to be quite rough. A guy's cock isn't fragile, its pretty tough. When you first start, pay a lot of attention to the head with your tongue and lips. Massage and squeeze his balls with your fingers. Use eye contact-watch your guy's face, act as if he's the most important guy in the world. Once you've got a rhythm going, settle down to a steady pumping action, mouthing his foreskin as far back down his cock as you can in a firm, tight action. You can use your hand in addition to your mouth. Pause occasionally, and go back to teasing the head again. Don't let it all get too wet and lubed up. If there's no friction on his cock head it will take him ages to cum-you'll get tired and he'll get fed up.
You'll know when he gets to the point of no return-his breathing will be labored and he may be pumping faster, etc. Once he gets to this point, DON'T STOP, keep it going until he cums. You will not be popular if you stop at this critical moment!
You ought to consider the position you take up. Kneeling on the floor in front, with him standing, gets uncomfortable for you if it goes on for long. I like to lie flat on my back with my girlfriend kneeling with her knees either side of my head, facing my feet, leaning forward. This is more comfortable for her, and I can look up between her legs, or she can dip her hips down so that I can give her oral sex whilst she's giving it to me.
When he cums, if you don't want to swallow it, you could open your mouth and show him his own cum, then slowly dribble it back over his cock. This sounds yucky, but it's pretty sexy actually.

A lack of confidence is reasonable. Your best bet, is if you want to do something competently, read up on it beforehand, read advice, and other people's experiences. When you read that others have similar doubts and that they weren't always needed, I think it'll give you a bit more confidence.

If you go slowly, consciously, looking for feedback from your romantic partner, I really don't think there's any risk of you biting them. You control the muscles in your jaw after all! Generally I have read that one tense to bring the lips in to cover the teeth so that if one were to tighten too much, it would not risk scraping.

Even presuming you did somehow do it, it would not be the end of the world. He's not going to hate you, and if he did hate you for a mistake then he's too judgmental and not a good guy to be with anyway. It's not as if it's going to cause any permanent harm or anything, it's a huge leap from a little scrape or bite to outright dismemberment.

Just don't jump in too vigorously with what you think will please him, don't feel a need to perform with gusto like some porn actress. Believe it or not, a lot of guys dig tentativeness, and would much appreciate competent slow tempo to rushing into things and being someone you're not, of disconnecting with it and being mechanical. Ideally I think he'd want you to enjoy it as well, for the act itself and not simply due to it satisfying him. Would you?

I pasted most of the following from a previous answer of mine that got favorable reviews. Have fun and thanks for all your hard work. World peace is just a few Blowjobs away.

Practice, Practice, Practice. Your thumb and fingers are a small, but good practice "tool" or buy a cheap dildo. First of all, a blow job is a replacement or a convenient pussy - warm, wet and soft. Start slow and stay slow and finish with a quicker pace by hand or mouth - your choice. A good technique for an average size (6-7 inches) is to simultaneously go down with your mouth while coming up with your hand and meeting your lips with your hand - then reverse. You actually suck on the down stroke and just let it slide out on the upstroke keeping the tongue in constant contact. As you progress with experience, the tongue can do wonderful things on both the up and down strokes (swirl around it, swab it with a big wet "fat" tongue - or make it hard and pointy and try to dig a groove into the underside of the penis with it) The simultaneous squeezing pressure of your hand will make it seem like you are sucking harder than you actually are or think you have to - it doesn't take much, but remember you are SUCKING on the penis. I never really understood why it is called a "Blow Job". This sucking down and pulling up technique also helps you keep from becoming tired - as you are not always trying to "deep throat". Do this simultaneous hand/blow job technique for about 7 to 10 strokes (thats 7 to 10 ups and 7 to 10 downs), then release your hand grip, slide it down to his balls and gently caress and tug on them. When you have gotten to the balls, now is the time for a very slow double/triple attempt at a deep throat. Go down as far as you can without gagging (remember to practice! ) Once you have made 2-3 deep attempts, move your hand back to the shaft and begin the simultaneous hand/blow job again for another 7 to 10 strokes. Practice until you can do this without really thinking about it. As for your jaw when sucking and releasing, try to keep it in an overbite (top teeth in front of the bottom teeth) position. This will help relieve fatigue on your part and naturally opens the rear of your mouth/top of your throat to help prevent the gag reflex. It also naturally causes the rear or base of your tongue to pull back a little to help cover the gag reflex too. Also remember that teeth cannot be avoided unless you wear dentures, in which case remove them first. Otherwise, don't worry too much, just try to not wear out grooves in the same area by raking your teeth over and over in the same spot. You will know he is coming when his dick swells even more. DO-Practice. DO-Stay Warm, Wet & Soft. DO-Mix it up. DO-Make some noise (moan, slurp, hum - BJ's are also called Hummers for a reason) DO-Bite (gently and without malice). DO-Vary the pressure of the hands and mouth. DO-More of whatever elicits a groan. DO MORE!

Hmm...shame you didn't get to the finish. Finishing him off is the big prize. It always makes me feel powerful knowing that I've taken him to a higher level. Don't you have somewhere private you can go?