A recent article by Jessica Stillman in Inc. magazine summarizes a recent Quora posting on what can you can do to get smarter. In short:
1. Be smarter about how you use your time on the Internet. Think more TED talks, Khan Academy and (presumably, Inc. magazine) and much less YouTube, Farmville and Cracked.com.
2. Write 400 words a day about something you learned that day.
3. Make an "I did it" list to remind yourself of your accomplishments.
4. Play games: chess, Connect 4, bridge, (MtG, anyone?).
5. Surround yourself with friends who are smarter than you.
6. Read a lot. A lot.
7. Explain what you've learned. You don't really know it until you can teach it to someone else so they will understand.
8. Do random new things. You never know how what you learn will help you down the line.
9. Learn a new language. (I hope programming languages count!)
10. Take some time to digest what you've learned. Sit and think (or exercise and think.) Spend time thinking.
I'm going to start with #2 tonight.