Simply put, doing unique, random, different, and ridiculous things is a good way to exercise the mind and promote new ways of thinking about the world around us. One hour of increased brain activity via thinking a lot or experiencing new stimuli can make you smarter, more energetic, more creative, more sociable, and more open to new experiences and ways of thinking. Here are some of the endless numbers of activities that can stimulate your brain. The key ingredients are to to be open to new experiences, and changes in previous ways of thinking about these experiences.
Not sure how sure (or scientific) are these claims, but fun anyway to follow some of the suggestions such as:
 Stimulate your eyes in new ways. Look at different art sites such as deviantART or Seventh Complex Digital ArtWorks. Go to a cheap or free art gallery. Even if you think it's bad art, it can still be stimulating and thought provoking.
 While waiting (in line at the bank, a coffee shop, a restaurant, the grocery store, or waiting for someone to pick you up, or a show on TV to start), ponder things, calculate, memorize. You can, for example, memorize digits of Pi (you can get to 50 in a matter of hours, 200 in a matter of weeks),...
 Take unusual classes. Find a community college or community-based educational program near you, pick up a catalog, and open your mind to learning things like Art History,...
 Learn how to write backwards. Leonardo DaVinci, the quintessential Renaissance man and a jack-of-all-trades, wrote all of his notes backwards so that they could only be read with a mirror.
 Try foods you have never tried.
and many more. [The list suggested 42 things you can do.]