Oh I have this great trick that I like to do when a guy is asleep and I wake up horny and am unable to fall back asleep.
I'll cuddle up to him and lightly "accidentally" brush my arm against his penis or I trace my fingers right along the top seam of his pants until he starts to get hard and wakes up, at which point I get on top and...well you know.
Usually, if we're both awake though, I'll get him to spoon me and then start arching my back against him so he can feel my ass grinding against his crotch. Then I expose my neck so that the guy can bite it, which I LOVE. This usually gets the point across, lol.