Google has a few search options that many people are not aware of. First, Search Options, a collection of tools you can use to filter your searches: by type (reviews, videos, images, etc.), by time (most recent, a week ago, etc.), related searches that you can use to expand your query, and more. You can access these expanded search options by first typing in your initial query, then clicking on the Search Options link. My favorite? Finding images from the text on the page that your search results are on. Next, the well-named Wonder Wheel!
The Wonder Wheel takes your search phrase and shows you related phrases; for instance, my search for "tennis" brought back "history of tennis", "tennis rules", "wimbledon", etc. Last, but not least, the Timeline.
The Timeline shows you searches for your query in a chronological manner - you can see all the search results for tennis here go clear back to 1780!
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Wendy great article, I use it to gather semi-related keywords for my advertising account. For those who are still confused on how to use it, here is a great tutorial: http://www.wonderwheeltool.com
Good Luck.