there are many ways that you can use to help increase your energy levels during the day, the most important being having a regular sleeping schedule. go to bed, and get up at the same time every morning and night, this will help regulate your energy levels and will even help your concentration. in conclusion to this don't eat two hours before you go to bed, as it can disrupt your sleeping patterns, and try to do something calming before bed, like reading, light stretching, or meditating. Tv, video games, and computers can also affect how well you sleep.
have fruit for breakfast in the mornings, or other healthy choices like oatmeal, the protein and vitamins in the fruit and oatmeal will really perk your system up. it's always important to have a good breakfast.
exercise in some form at least an hour a day, preferably before you've eaten, as a full stomach can make it uncomfortable. it doesn't have to be rigorous activities and it doesn't have to be all at once. take a fifteen minute walk, play a game of pool, go dancing, or even do some jumping jacks when your feeling sluggish.
keep yourself hydrated, drink lots of water and try to avoid sugar and caffeine, they will perk you up for a while but you will experience a 'crash' later. there are juices that can help you experience a natural rush that your looking for, orange juice often perks me up.
and of course, make sure that your lethargy isn't something medical. if your so tired during the day that you just can't do anything for long periods of time, days or weeks, it could be a thyroid, or a chemical problem, or even Anemia, so make sure you stay up to date on your doctors appointments.
i hope this helps^^