One great way to improve your mind power is to work on your skills of intuition. Intuition is basically your ability to predict an event or other occurrence before it happens with no prior knowledge. Think of those gut feelings you get and you have a good idea of what it is. There are lots of interesting ways to improve your intuitive skills and to enhance your mind power.
For the book fan, one great way of working on intuitive skills could be to read lots of mystery novels. By reading many books that follow the standard crime novel formula (crime, investigation, outcome), you can see how certain pieces come together and point to a character within the confines of the novel. Not a fan of fiction? There are lots of nonfiction mystery and true-crime books available. Be sure to vary authors so as to challenge yourself. A similar exercise can be done with television crime dramas or movies.
There are many games on the market that can help increase your mind power and intuition skills. While some of these games are not marketed with this purpose, you will be able to find many that were created with the brain in mind. Card games that test memory will be a great way to work on your mind power. You can certainly find games that test intuition online. Just be sure to avoid the gambling websites.
Challenging yourself in other ways is only bound to help your mind power. If you feel comfortable taking on a new project, by all means, go for it. Try something handy around the house, or perhaps try your hand at art. A new hobby can refocus your thinking, while following unfamiliar instructions can only aid in strengthening your intuition. Start small. A jigsaw puzzle could be a great place to begin. Matching the tiny pieces together (with or without the aid of the picture on the box) can help you focus on something smaller and more detailed, thus causing you to concentrate in a different way.
However you choose to build upon your already existing mind power, you can only benefit. As you work on your intuition, you will undoubtedly feel the satisfaction of guessing the whodunit more and more frequently. Of course, there are larger, more important outcomes from developing stronger intuitive skills, but there are certainly worse places to start your growth. Have fun with it, and notice as the results increase with more practice.