high five or wave?

Have you ever been stuck in the awkward situation trying to figure out if somebody is going in for a high five or waving? What do you do? If they're trying to give you five and you 'em him hanging, they feel awkward. If you go in for the five and they're only waving, you feel like a fool. It's a tough situation. I like to do is go ahead with the five. I'm pretty comfortable feeling like a fool, and I feel like fives are used more sparingly than they should be.
The most awkward greeting situation is the hand shake or hug decision. They're holding the hand out and you don't know whether to shake or hug. That one is a little harder. It requires that you do some evaluation. If you knew them well enough to go for the hug, I say go for it. If not it could get weird. You don't want to get stuck in the middle. Then you get the weird hug/handshake hybrid where you're holding half a wrist and have a mouthful of shoulder.