Hi, I thought you may like this Mentalrobics exercise from Braingle.com:
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Think Around It

When you learn a fact, there are many associations that are learned along with it. The more associations you have for a particular fact, the more likely you are to remember it because each association acts like a cue to remember the original information. You can use this idea to help you remember something that is on the tip of your tongue. Try to recall everything that is related to the idea. Chances are that something you DO remember will lead you to what you DON'T. For example, if you are trying to remember an actor's name, try to name all the movies that he has been in and all of his costars. It's very possible that in doing this, the name will just pop into your head.

The context of where and how you learned a piece of information is also stored in your memory. If you are trying to remember something that your math teacher taught you in class, try to picture the class and the circumstances surrounding the time when you learned it. This might cue your memory.
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For more mind exercises: http://www.braingle.com/mind/