Aim to educate yourself. Keep in mind an education isn't the junk you are forced to do in school for diplomas and degrees; it's an understanding of the world around you. People who are naturally curious for some reason begin to stop asking questions the moment they hit school. The truly brilliant mind however, always questions their world and tries to make sense of it. That is the secret to "genius".

Work on your vocabulary. Use a few definitions from the dictionary each day, or subscribe to a "word-of-the-day" service online. You can also take the vocabulary tests in Readers Digest or buy a book on increasing your working vocabulary. Read the dictionary one letter at a time. This will take you at least a year but you will grow intellectually.

Read a variety of books. Reading a lot is often described as the secret to intelligence. The smartest people in the world tend to read every single day. You may not always enjoy it, but reading will open up your mind to a variety of new ideas and experiences. Keep your reading diverse by reading books of all genres including non-fiction.

Educate yourself about the world around you. Cultivate an interest in subjects like current events, interesting facts, funny and inspiring quotations, good books and movies, scientific studies and interesting inventions. Educational television, like PBS, is a great way to learn. Learning to think critically about the world around you by being aware of cause and effect in events will make you much smarter.
If you can read much faster than you can speak, it is much more efficient to read a book, or better yet a non-linear electronic document like a wiki than to watch a show for all but the most intellectually demanding or video-dependent learning. Commercial television is particularly bad because its ultimate purpose is to do just enough to keep you at the TV and its ads, not satisfy