In life, we have all kinds of teachersfirst-grade teachers, biology teachers, ballet teachers. While they may have been responsible for teaching us how to read, how to dissect a frog, or how to do the perfect plie, they also taught us perhaps one of the most important lessons about aging: Teaching can save your brain. You're far more likely to retain information if you have to explain it to somebody else. The degree to which you can effectively explain information indicates how well you've actually learned it.

The lesson: Take advantage of mentoring opportunitieswhether it's instructing a class in your favorite hobby at a community college, or inviting the neighborhood teens over to teach them how to change a tire or make a souffl?. Teach the next generation, and you'll power up your own generator.