With our brains, it is the simple matter of what you don’t use, you lose.
To maintain good brain health it is necessary to stretch it, and constantly challenge it in new ways to make sure that it remains alert and able.
Do crosswords, Sudoku and other puzzles. This sort of mental activity is constantly exercising your brain, making it think, probe and engage in problem solving activity.
This helps your brain retain its processing ability better and it is able to react quickly and positively in real life situations as well.
Take Quizzes, Vocabulary tests etc. This not only tests the sum of your knowledge, it also helps with recognition, and recall which are good for revising and retaining information in the brain.
Scoring well on a test or quiz not only exercises your mind, you also get the added satisfaction of knowing when you do well!
Read; a lot! They say no reading goes to waste; and perhaps that is true, because all information will at some point of time come in handy and useful.
Read fiction, nonfiction, journals; whatever you can lay your hands on. This will constantly give you new information, help you learn new things and widen your horizons to include new things.