Begin in the morning.
You should start off your day by exercising in the morning after a light pre workout breakfast because the adrenaline will give you an extra energy boost to help keep you alert for the whole day.
However, if you are unable to complete your workout in the mornings, just be sure to do it at least 4 or 5 hours before bed, to ensure the adrenaline doesn't keep you awake.There are also certain drinks that should be avoided for a more desirable night's sleep.
If you enjoy drinking large quantities of alcoholic, or caffeinated beverages, cutting back is something you should seriously consider if getting more sleep is important to you.
Additionally, naps should be avoided because they make it harder to fall asleep when you actually want to sleep through the night, but if a nap is absolutely necessary it should be limited to 20 minutes or less.