Kudos to you for being proactive! Here are some things that will give your brain the best chance at serving you well through the changes to come.
Challenge your brain. In order for this to happen, you have to be learning something new. A language, sport, musical instrument, craft—pick something. It doesn’t matter whether you’re good. Only the learning matters.
Get aerobic exercise. Research shows that even moderate exercise improves cognitive performance including memory, regardless of your age.
Eat foods high in antioxidants. Antioxidants help with cognition because they lower inflammation in the body. You can find them in many fruits and vegetables, but blueberries, strawberries, raspberries, goji berries, dark chocolate, pecans, spinach, beets, and red cabbage are particularly good choices.
Drink less alcohol. Specifically: don’t binge drink. Over time, binge drinking can damage the hippocampus, which is important to memory.