Good question to ask! Simple things like memory games, getting some good exercise, traveling, healthy diet, making social connections and even watching jeopardy can simply help with brain function.
As for supplements you need to be careful which supplements are going to work for you. If you do a google search for supplements you'll get a lot of websites selling the same thing. I've tried a lot of them and some of them work, some of them do not. I've had most success with a supplement called Prevagen http://www.prevagen.com it targets the inbalance of calcium within your nervous system. Pretty interesting technology and it seems to be very powerful and very effective. My memory was improving within the first month.