I always have the alarm clock set. If I feel too tired in the morning to get up, I set it for an hour or two later. That way, the noise will get me up and I almost always get up after that second alarm goes off.

Something else that works for me is I will get up as usual in the morning, telling myself that if I REALLY feel tired later I can take a nap. So I go about my day as usual, getting things done, and if I later feel the need to sleep, I take a nap (setting the alarm clock for about 2 hours later). That way, I feel like I've gotten stuff done, AND extra sleep!