Searching for an available trademark can be accomplished in a variety of ways.  
The PTO has information concerning all federally registered trademarks and
information pertaining to all federal pending, abandoned and cancelled trademarks.  
This information is available at (as well as various forms and
informational pamphlets).  The major drawbacks to the PTO’s database include the
limitation that no state-only trademarks are included and any non-registered
trademarks are not on file.  Both state and non-registered trademarks can result in
legal and marketing problems (i.e., having to change the name of a product after it has
been introduced) if you use the same or a similar trademark on the same or similar
goods or services.  State trademarks can be searched on commercial databases, such
as the Lexis/Nexis service and by trademark search companies, including Thompson
& Thompson.  Non-registered trademarks can be searched, to some extent, on the
Internet and other commercially available databases and materials.  

    When performing a search of a possible trademark, it is important to consider
variations in spelling and sound that could result in problems with registering the
trademark or with other companies.  In addition, where appropriate the trademark
should be broken down to its root form and stripped of any descriptive words.  As an
example, a search of the trademark “All-Nite Lite” for a flashlight should search All-
Night, All Night Light and various other combinations, in addition to the trademark
itself.  Foreign words should be searched in the foreign form and in the English
translation of the word(s).  Trademarks having drawings are generally much more
difficult to search.  The basic approach is to describe the drawing in words and then
search those words in the appropriate database categories.