Most women *claim* they know how to suck cock really well. As a woman, I KNOW I like to know I'm giving my partner what he wants, and through trial and error, as well as many conversations with me I have come up with what most men agree are the perfect behaviors for a woman performing fellatio.
First and foremost, take the time to appreciate and enjoy a man's penis, it's a beautiful piece of anatomy, the skin is incredibly soft and sensitive, the shape, the feel of it in your hand, the soft texture of the head against your tongue. Appreciate how sensitive the head of his penis is and enjoy his desire to share that part of himself with you.
Most women think "I'm giving myself to him" but they don't stop to think that MEN are giving themselves to us also. Appreciate that. Yes, men tend to have more partners than women, but that doesn't negate the fact that he is still giving himself to you and TRUSTING you to have his very sensitive cock in your mouth with your very sharp teeth! Once you realize that most men are very sensitive about their size and shape in relation to other men, then and only then, you can really learn how to give a good blow job.
1. Be in the mood to please him orally. If you aren't really into it, he's going to know and it's going to diminish his experience. As much as you want him to WANT to eat your pussy, he wants you to want to suck his cock.
2. Take your time; get into a comfortable position where you can get the best angle with his cock. Make sure you're in a good angle for the particular man by seeing if you can deep throat it from the first position you chose. If you can't, rearrange yourself! Men appreciate your desire to move yourself into the right position to please HIM. Just as much as they move around when they are reciprocating. Some women can't deep throat a larger cock and that's ok with men, they know it and love that you are willing to try!!
3. Once you find that right position, give him a quick suck, gently, draw your mouth slowly down his shaft as far as you can without gagging yourself, and then slowly come back up. Place your hand around the shaft gently and hold it in place while you give him a cute, coy grin. Let him know you are enjoying him! No matter how big a man's ego, he needs to be reminded he's wanted and that you LIKE his cock.