Stop using stimulants during the day, get excersise every day
for about 30 min, eat well, dont eat right before
sleep.
The hard part about all of that is that it often requires changes to many engrained habits. Its easier said then done to really get yourself up and go work out for a half hour, or cut back on drinking that coffee during the day.
If none of those things seem to work its probably importnat that you talk to a doctor about it.