Talk nicely to her.....really a no-brainer but this basic necessity is surprisingly elusive to men.
Women are taught to reject themselves and to feel inadequate. The message is we are never slim enough and pretty enough and even aging super models now quietly admit they are feeling the pain of not being able to command and manipulate the way the used to...poor dears....my point is our external shell is transitory but if you want to have enduring good sex with her make nice and compliment her. Reinforce anything positive you see in her. Such a simple act will get you results, a lover that will be far more enthusiastic towards you.
I am convinced some guys are unkind so they can rationalize their partner's lack of enthusiasm to go cheat on them. It is very basic...if you are unkind to her she will not want to have sex with you let alone doing anything to please you.
http://evyestanten.blogspot.com/2011/01/how-to-please-her-part-2-by-evye.html