I use an alarm clock, just in case my own internal clock runs out of batteries I've found that I have some of my most vivid dreams between snoozes. I know hitting snooze isn't good for me, but I limit myself to twice before getting up. It's amazing how long you can dream in the span of 9 minutes.

There's more info around here about time manipulation in dreams. I haven't experimented with it personally, but I'm sure there are people around here who could help you out with that.