Deep-throating

Deep throating is a form of fellatio, when all of an erect penis is placed inside a partner's mouth. The penis will enter the throat. The person whose penis is inserted is normally referred as the receiving partner, and the person who performs deep-throating is referred to as the giving partner.
It is difficult for most people to perform deep-throating, because of the natural gag reflex that happens when the soft palate is touched. Different people have different sensitivities to the reflex, but some people learn to suppress the reflex. 
Usually, the giving partner's tongue is immobilized during deep-throating and they also are not able to suck.
Sex positions.
The position of both partners is important in performing deep throat. For deep-throating, the giving partner's mouth and throat will need to be aligned (made into) into a straight line, and he or she will need to respirate through the nose. It is important for the giving partner to be in a position to control any pelvic thrust during deep-throating, to be able to pull the penis out if needed; and for the receiving partner not to thrust, as during irrumatio.
"Over-the-edge" is a common position for deep-throating. In this position, the giving partner lays on his/her back with the head hanging off the edge of the bed and the receiving partner stands or places himself on his knees in front of the giving partner, with his penis at the giving partner's mouth.
Another position used for deep-throating involves the giving partner sitting on the receiving partner's chest, with his feet or penis in front of the giving partner. 
The 69 position is another position for deep-throating.