A link to this Google Cheat Sheet is availabe at Google under Advanced Search. It’s such handy information that I thought a post on it alone would be handy. You can bookmark the site on your own browser, or use it to make a printout.
Most of us just plug some search terms into Google and let it go at that, but if you become familiar with only a few of these other searches on Google, you will greatly expand the usefulness of your Google results.
For instance, you can use OR to get one term or another; you can get rid of a common term by using NOT; you can get a definition; you can do a specific site search; search between a range of months.
There’s more but look for yourself.