1. Lift weights
Any exercise is good for mind and body, but weight lifting and resistance training may offer special benefits, according to at least a couple of studies on women.
In one study of 65- to 75-year olds with normal cognitive function, women who exercised for an hour once or twice a week, using dumbbells, weight machines and other calisthenic exercises significantly improved their long-term mental focus and decision-making. The control group — which did not see the same brain benefits — did "balance and toning exercises" including stretching, range-of-motion.
Another study, of 70- to 80-year olds with mild cognitive impairment, showed cognitive improvement among women who did either resistance training or aerobic exercises. Men weren't included in that study, but other research involving both genders finds that strength training helps preserve or improve memory.
No joke: Humor is healthy. A hearty laugh provides short but similar benefits of aerobic exercise for improved heart (and brain) health and immunity. Other benefits: Laughter elevates the production of neurotransmitters linked to improved memory and alertness while decreasing stress hormones that can cloud thinking. And when listening to jokes, as you wrestle to understand the punch line, areas of the brain that are vital to learning, creativity and decision-making activate, much as they do when working out "brainteaser" crossword puzzles and Sudoku.
3. Take a nap
In addition to improved daytime alertness, good sleep — night after night — helps keep memory and learning well-tuned. But even with Rip Van Winkle-like nocturnal habits (and certainly without), consider a regular afternoon nap for about 90 minutes. It costs nothing but time — and the payback, according to studies, could be significant. Compared to non-nappers, those who partake in daytime zzz's display measurable improvements in tests gauging decision-making, problem-solving, creativity and even tasks like recalling directions.
Studies find that daily meditation can strengthen connections between brain cells, increase growth in the part of the brain that controls memory and language, and may even bolster the ability to process information and make decisions more quickly. There are various forms of meditation, but most involve spending 15–60 minutes — best if done at least once a day — of focused attention on a word, object, sound or even your own breathing. Classes help, but for cost (and other) consciousness, consider free "how-to" videos and help available online.