Sometimes it can be a chore to stay mentally sharp during the workday or during other parts of the day. However, there are many ways to increase your alertness and productivity all day.

Make sure you get enough sleep at night. We all know it's important, but many of us don't know just how important: Sleep is the most important factor in increasing alertness, according to University of Florida psychology professor Ira Fischler. Although the amount each person needs is always different, The National Sleep Foundation suggests 8.5 to 10 hours for teenagers and 7 to 9 hours for adults.

Fischler says that if an activity stimulates your brain activity, you can increase your alertness to perform other tasks. Try learning a new language or practicing puzzles. Games and challenges like crosswords, Sudoku, chess, monopoly, and strategy games all work (exercise) that side of your brain. Learning a new language has proven to be the best way of exercising your left brain because it uses so many different skills and so many different areas of the left brain.

Avoid a heavy lunch. A lunch high in carbohydrates, makes you blood focus in your stomach and takes away from your brain's fuel. It also increases serotonin levels in your brain making you drowsier. Eat protein-rich foods that increase your dopamine and norepinephrine levels, making you more alert.

Power nap. Napping is always a good thing. A fast relaxing nap can really increase your mental functioning, especially if you are sleep deprived. A 10- to 20-minute nap in the workplace can increase your productivity and reduce errors made on the job, according to the National Sleep Foundation. Be careful, though; a nap that lasts longer than 35 minutes especially if you are sleep deprived, doe NOT benefit you, it makes you feel more tired. Also, do not have a nap too close to your bedtime. It can mess up your sleep patterns and make it hard to get to sleep.

If all else fails, turn to caffeine. The National Sleep Foundation says it's acceptable to have three 8-oz. cups per day. It takes about 15 minutes to half an hour for the caffeine to kick in and the effects can last more than 6 hours. Don't take more for any reason. Higher levels of caffeine can increase your brain activity in a bad way. It can make you jumpy, and hard to concentrate. Although coffee and power drinks get a bad reputation for their high sugar content and their addicting nature, Fischler says caffeine in balanced doses can be effective.