What is your typical warmup for a session or a race?

I know this is a very newbie question, and there is ample info in swim books/sites about this, but I'd love to hear from REAL SWIMMERS like you, thank you very much. What works for you? Lately I've been doing a series of 200m to 25m swims, usually totalling 800m, as a warmup. Example: 2x200m + 2x100m + 2x50m + 4x25m, starting very easy, ending at "fast" pace. In the future I hope to incorporate drills into the warmup, but I don't have a clue yet. :)