Oh no, my pants are too tight! Can you take them of for me?

Depends on the situation and your boy, but in my experience, it's the little details that matter.
What has worked for me:

- Kissing. No-brainer. I like kisses that start out gingerly and turn devouring. Again, details matter. What is she doing with her hands? And so on. Personally, I like to be lifted up by the waist while kissing. Or literally swept off my feet. I think it's fairly easy to show your desire without going straight for his dick.

- Compliments. Again, a no-brainer. Not only girls like being complimented on. But perhaps you don't want to praise his great personality or his quick wit when you want to get him into bed. I like being told that I'm attractive. I get a kick out of being grabbed by the hips and told that I'm looking sexy in those black boxers.

- Realize that you have an entire guy at your disposal, not just his genitals. Touch those other weak spots first. Every guy is different when it comes to those. I like being hugged from behind and having my neck bitten. To me, that's a surefire sign of things to come.

- Words. You don't need to walk over to him and say "nice boots, wanna fuck?". In fact, I strongly prefer not to be told that. Indirect communication works equally well! Involve him in your fantasies. Drop hints. Speaking of your fantasies: I love to be told her fantasies. It doesn't even have to be done verbally. Even a drawing can help.

And as said earlier, a lot depends on the situation and your relationship.
Do you have any place where you touch him, a sound you make, or something you say when you're in bed together? Do something that reminds him of the most passionate sex you've been having, and it'll be fairly clear to him what you want. For example, to have my face licked by her is one of the biggest turn-ons on earth. Guess why? Yeah.
Do something that plays to the situation:
Cuddling on the couch? A fun way of turning that into a seuxal situation is tickling, if done right. I'm very ticklish around the sides of my torso. Groping me there is an easy way for her to turn the situation around. Even pulling up one of my arms and burying her face in my armpit has worked in that department.
Going to sleep? We always go to sleep with her spooning me. If she wants me to know that she "wants something", she just needs to run her hand along my thigh and ask me "whether I'm asleep". COUGH.

So, all in all: Use your imagination. Nothing hotter (to me anyways) than when my girl gets creative. Do something that fits the mood and your boy. Don't count on one-size-fits-all. It doesn't. 'cause, y'know - I would totally not get turned on by lingerie. Yawn! I find her naked body much hotter than any piece of cloth.

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PS: I've never gotten head while asleep, as I don't like being blown, but as for other forms of stimulation while he's asleep - that can be hit or miss. Chances are, the timing will be off! Whoops!

Men fail at catching hints. Even if we do catch one, we're going to think "Oh I must have misinterpreted that.". Gotta just tell us.