I found the sleeping bag was causing me to keep awake, I didn't know it then but it turns out I have some mild claustrophobia. I recently switched to the GoLite Quilt which lets me shift around without creating cold spots or anything. Made a big difference.

Some compiled suggestions for everyone's benefit:
-take it easy on the sugar and caffeine after x:00 (find your cutoff time, mine is 3:00pm)
-don't eat a big meal right before bed
-no tight clothing or restrictive sleeping bags
-try some drugs at home if you need to (benadryl, pot, alcohol, whatever works for you and your morals)
-ear plugs help if you're prone to waking up every time a tree creaks or a wave crashes.
-make a note of your thoughts before you go to bed. If you're not trying to remember things, your mind might not be so active
-try to emulate some of your routines at home. Walk the dog, have a cup of tea, read a book, contemplate your navel.. whatever you normally do before bed.
-if something about your camp setup is bothering you, get up and fix it. Lying awake all night worrying about it is worse than a few minutes freezing yourself resetting your tarp or hanging your food higher.