Well, there's a list of turn ons in 'pleasing her,' so I figured why not have one here.

What my girlfriend does that turns me on:

Those little noises she makes, the tiny moans and gasps... Those are amazing.
In fact, just about anything she does that lets me know that she's turned on is in turn a major turn on for me.

Skirts can be a turn on. Not miniskirts, I mean ankle-length. When my girl is wearing a skirt and she sits or lies down, and her legs suddenly appear, my heart starts beating faster. Something about how it's only a layer of fabric draped over her legs. Skirt without panties: Double sexy.

I also find her feet sexy. Not to the level of a paraphilia/fetish, but it does arouse me a bit when she goes barefoot.

It's highly arousing when she struggles against me, or against the ropes when she's tied up. She enjoys struggling. :)

On the other hand, it's also extremely arousing when I begin to tie her up and she simply assumes the position I'm going to tie her in and waits for me to finish. Her anticipation is thick enough to taste, and it tastes good.

Let's see... What else...
When we are making out, the more active she is the better. The more she does with her hands, the better. Also, while usually I am the one going over her neck and ears with my mouth, sometimes she does this as well, and it's highly arousing. Especially my neck.

When we're alone together and she lies down on her belly, it's quite sexy. That particular position is an invitation to get on top of her, a position in which my weight holds her firmly down, something she and I both enjoy.

And last but not least, at times she will do or say something which she knows will get her a spanking. I know she's doing it because she WANTS her ass spanked/flogged/paddled, and that fact is a turn-on.

So, dudes, make your contribution! Set down your turn ons in words, so that a fellow dude may soon have the pleasure of being with a better informed partner! ;)