Those infamous leg cramps

I'm finally starting to get those infamous pregnancy leg cramps that you always hear people talking about. For awhile, the main problem was just my legs falling asleep if I sat still too long, but now I'm getting these too. Uggh. I've noticed that I have to be careful not to flex my legs while lying down, or I'll get them, and the only way to cut them down to size is to leap out of bed and launch myself into a standing position as fast as possible. I think they're circulation-related, but I'm not sure what, if anything, I can do about them. Just one of those things, I guess.