How do you please a Dominant Top?

if the sex is 'great' then your already doing something good. Continue doing that AND other things. Focus on 'him', make him feel like he's the only one. Talk to him as a 'sub'. Not sure if you do the 'yes sir, no sir' bit. The more you make him feel like he's the best the more he gets off on it.
 
when i have been 'the sub', i have made my bull top think the world revolves around him and his penis. that is mostly what he is thinking of. i also make my ass available to him at all times. but i never 'come on' to him. . . he is always the aggressor.
 
You must make feel that he owns your ass, everytime, anywhere, you must be ready to please him. He must see this look ( of lust) on your face everytime he fucks you. He must feel how much you care about his pleasure. Finally don't finish untill he is fully satisfied.
 
you could try reading: The Leatherman's handbook, By Larry Townsend. It is a good primer in old guard leather.

you could go to a leather bar in your area, or look into leather groups in your area. . those people know about kink culture and give you more information.

best of luck.

Misterslave.