I've had sleep "issues" as long as I can remember. The Paleo diet helps a lot as does regular exercise. Though if I am strict very low carb, after a while (few weeks to a few months depending on exercise levels), it seems like I get out of the happy zone again. So the best routine for me to have good sleep (and generally good energy / health / mental function) is the Paleo diet with either moderate carbs (50-100g per day), or very low carb but with a decent amount of carbs about 2x per week. I lose weight best with very low carbs (<= 25-35g per day), so sometimes I have to choose between sleep and weight loss.
I have a tendency towards bimodal sleep, especially as I get older. Interestingly, my dad was the same way, as was my grandfather on the other side of the family. I wonder if it might be genetic. If I fall asleep in the 9:00-10:30pm range (early for me) I almost always wake up at about 2-3am and am completely unable to go back to sleep, I'm wide awake. I've learned that I should just get up and get out of bed and do something for a few hours, usually I will read, or post to PaleoHacks :-). Then at about 6:00am, I get tired again, it hits me suddenly, and after being wide awake for several hours, I can fall right asleep. At this point I can sleep 2-3 hours. This adds up to a full night's sleep, but obviously sleeping from 6-9am gets in the way of a job or getting the kids off for school, so what often happens is I skip the second phase and don't get enough sleep.
To avoid this, if I can force myself to stay awake past 9-10pm and then fall asleep in the 11am-2am range, then usually I'll sleep until 6-7am, which varies from almost enough sleep to plenty of sleep. I would prefer to get 8 hours every night but my long-term average is probably closer to 6 hours.
In any event, I almost always wake up several times during the night, and almost always at 4am. My brain is obviously very active at that time and that is when I usually have a lot of anxiety about something or other, which I would prefer to process sub-consciously but obviously my brain has other ideas. If I have something particularly stressful going on, this will wake me up and I won't be able to go back to sleep.
I have tried all kinds of sleep supplements / meds such as Tyelenol 3 and melatonin, which both gave me weird hallucinations and left me feeling drugged all the next day. I am scared to try Ambien after hearing stories of people waking up and cooking a pound of bacon and not remembering it. Alcohol doesn't really help, and the leafy green just stimulates my brain more rather than making me sleepy.
About the only things that do work for me are diet, exercise, and trying to keep a pretty consistent sleep schedule.