So you want to improve your brain? After spending a long time listening to people knowledgeable on this topic, asking questions, and reviewing all of the most recent literature (try Google scholar to speed-read primary sources) here are some of the takeaways.
1. Drink plenty of water. 8-12 servings of water per day keep the brain and its protective tissues hydrated.
2. Exercise, improving your breathing and bloodflow. An action as simple as walking pumps blood into your upper body and head more efficiently than when you are at rest.
3. Maintain a 'Mediterranean' diet with whole grains, legumes, and olive oils
4. Use spices such as cumin, curcumin, and corriander (ingredients in curry) that have a known antioxidant effect, as well as dark berries such as blueberries.
5. Stay engaged with education, work that requires intellectual focus and concentration and socialization
6. Exercise your brain with demanding tasks or games that require a "shift" in attention and quick reaction, that can be increased in intensity, forcing your brain to adapt and rely on different neuronal arrays. Taking up programming or learning languages is an excellent way to supplement this.
7. Stimulate and unleash your right-brain by learning a new instrument, drawing, painting, or writing (blogging, even)
These simple tips, combined with regular laughter and joy, can help you stay focused and sharp for your whole life.