CHOOSE YOUR POSITION:
When giving a blowjob, you have to decide if you would like a passive or an active role in the process. First consider your preference. Are you going to have an attitude or a hard time if he starts to thrust his penis into your mouth? If so, you might prefer the active approach.
Have him lay on his back or sit in a chair. You will be able to control how much of the penis is your mouth at any given time. He might still begin to thrust or push your head down to get greater penetration, but you can use your hand to control the depth of the penetration. You can wrap your hand around the base of his penis and continue to focus on the tip. As long as you suck on the head, he will continue to enjoy himself. This way you will control how deep his penis is in your throat.
The passive role is only for those of you that can handle deep-throat. This might be a 69 position with him on top, or you sitting on the floor with your back against the wall and he thrusts into your open mouth. This is for people who have no problem relaxing the muscles in the back of their mouths. You can still play an active part in these positions by using your hand wrapped around the base of his penis to limit how deep he can penetrate. Use your mouth to suck on the head