
To know about the Basics of the CAML query read this article.
Download Link
Use the following link to download the CAML Query builder.
http://www.u2u.be/res/Tools/files/CamlBuilderSetupv4.0.0.0.zip
Update: CAML query builder for 2007, 2010, 2013 and SP Online link
How to use CAML Query Builder...