Use information that has been peer reviewed, or examined for accuracy, by an editorial board.  Peer reviewed information is usually found in scholarly journals. Editorially reviewed information includes books by university presses and articles in major magazines.  Notice if the person writing the information is an expert who is recognized as an authority in the field.

Don’t use just one source. Use multiple sources and compare the coverage. Look for similarities and examine any discrepancies. 

If your topic is controversial or includes numbers and statistics, see if you can find another source to back it up that has the same numbers, or similar evidence.

Ask yourself if the person or organization responsible for the information could have an interest or agenda that is motivating their writing.

Be skeptical of commercial sites offering magic solutions to difficult problems.  You could check out some hoaxes at www.snopes.com.

Check information against what you already know and your common sense.  The more outlandish a claim is, the more research you will need to do to make sure it is true.