One of the main problems with deep throat i.e. taking in your partner’s penis as far down your throat as he can is that you have to overcome the gag reflex. The only way you can learn how to do this is to relax your throat as he pushes his penis further down. Try to keep your throat relaxed as he continues to push. Take it slowly and carefully and I promise you that practice will make perfect!
The other difficulty is negotiating the natural bend in your throat which is just past the back of your tongue, which leads down into your stomach. The best way of doing this is to lie on your back on the bed with your head hanging over the edge at a sharp angle; this way your throat and mouth is now in a straight line which will make the insertion of your partner’s penis a lot easier to deal with.
In this position, you won’t be able to move much at all aside from keeping your mouth closed and firm around his thrusting penis. So your partner is totally in control here. He will have to initiate all movements, thrusting and speed whilst you lay back and enjoy! For safety purposes, consider agreeing on a sign to indicate if or when things become uncomfortable for you.