1. Exercise. It does help. Not only does it keep you feeling fit, but the chemicals released in the process have been shown to improve cognitive performance. On an unrelated (but interesting) note, people who imagine working out for twenty minutes a day or more actually perform better in exercise tests than people who do not. Cool, eh?
2. Meditation. Again, it not only feels refreshing, but trains your brain to ignore distractions and perform more efficiently. I semi-regularly practice meditation and I find that afterwards I'm endowed with a keen sense of euphoria and concentration.
3. I drink green tea. I've managed to pick up some minimally-processed imported Japonica whole-leaf green tea and I must say, it is bliss in liquid form. The slight caffeine boost enhances cognitive performance, or at least it appears to.
4. Everything else: diversifying your habits, getting hobbies, coding, reading, organizing, starting new projects, communicating with people, writing, etc. all help to get the proverbial gears turning (churning?).
There are no shortcuts to a genius brain, however. Though if you work hard, work efficiently, and supplement your efforts with the activities mentioned in this article, you will most likely see a significant improvement in your mental faculties.