2. Approach the "new" often.

Why it matters: The brain loves novelty. Although different types of mental skills change with age -- for example, mental computations slow -- the brain never loses the ability to grow. And trying or learning new things builds new neural connections all through life.

Maximize brain fitness and the body will follow in kind, says UCLA's Small. Staying receptive to new ideas also fuels curiosity, open-mindedness, and creativity -- traits linked to healthier aging.

Unfortunately, habits also ossify with age, which can make us prone to dismiss new things or feel intimidated by them.

What to try: Work "mental aerobics" brain workouts into your day. You can buy software with puzzles to flex your brain or play games like Scrabble or Trivial Pursuit. Be sure to keep challenging yourself; move up to working harder Sunday crosswords or mastering an instrument with more complicated music.

Consciously pull out of familiar ruts: Listen to some music that became popular after your 20s and 30s, even if you don't think you'll enjoy it. Keep looking (and more important, feeling) contemporary by visiting a cosmetics counter for advice on fresher makeup, or try shopping with someone in their 20s or 30s to experiment with new looks in clothing or glasses. Travel to a new locale or to try a new experience (such as a dude ranch, eco-tour, or Elderhostel).

Explore adult-education classes at a community college or through your local parks and recreation department. Those over 65 can also find inexpensive, and often high-caliber, lifelong learning programs at local senior centers.