How can girls pleasure guys?

Well, it depends. Different guys have different ways to how they want a girl to pleasure them. For me, I like a girl to show that she really wants to have sex. she doesn't need to over exaggerate and shout so much [it gives me the creeps if she does that], but she must show through her expression that she feels a lot of pleasure, whether I am sucking her breast or eating her out. Also when she is giving me head or letting me penetrate her, i would like her expression to show that she is enjoying it as much as i do. For example, i like it a lot when she strokes her breast or nipples and licking her lips with eyes closed when I am penetrating her. Seeing that and doing the action really can give me the highest pleasure. It's best to talk with your partner about his or her turn-ons in a casual way, so that you will know better about him or her and your sex can be a better and more pleasurable one for both.