In all my years of performing fellatio, I have observed one constant, each man likes to be pleasured differently.
Women innately are good at multitasking, so clear your mind because that is going to be your greatest strength for this exercise.
It can be strenuous on the neck so try kneeling in front of him while he either stands or sits down with his legs open.
Find a comfortable position to do the act.
One thing all men seem to love though, is when you swallow their juices like unwanted gum.