When I was having a lot of trouble getting out of bed reasonably promptly in the mornings: practice getting out of bed - but not after just having woken up, that's what I was having trouble with in the first place. No, during the day, having been up for a while, go lie in bed for a couple of minutes with the alarm set, then get up when it goes off. Also, make this a pleasant routine with stretching, smiling and deep breathing.
I found this idea on the net here, which may have more details: http://www.stevepavlina.com/blog/2006/04/how-to-get-up-right-away-when-your-alarm-goes-off/
I tried it and it seemed to help a lot for a while, and I feel more in control of my weekend mornings.
I sometimes use a similar principle with stimulant drugs for ADHD (which are meant to be taken daily), waking 30 minutes beforehand. The main limiter there is that the overall effects are sometimes net negative, varying in a way that I partially understand, and so I won't want to take them daily.
I also recommend the app (for both Android and iOS I think, though I've only tried the former) "Sleep Cycle". You give it a 30 minute window, and it'll try to wake you up during the part of your sleep when you are closest to being awake, thus reducing sleep inerti...
Thus spake Eliezer:
It seems that many here might have outlandish ideas for ways of improving our lives. For instance, a recent post advocated installing really bright lights as a way to boost alertness and productivity. We should not adopt such hacks into our dogma until we're pretty sure they work; however, one way of knowing whether a crazy idea works is to try implementing it, and you may have more ideas than you're planning to implement.
So: please post all such lifehack ideas! Even if you haven't tried them, even if they seem unlikely to work. Post them separately, unless some other way would be more appropriate. If you've tried some idea and it hasn't worked, it would be useful to post that too.