To be successful in registering a trademark, it is important to select one that is not already in use for the goods or services you offer or intend to offer. The simple searching described here is no substitute for a fromal trademark search, but can certainly help you determine if there are any ready conflicts.
Start with a Google search (or use the serch engine of your choice) of the words you intend to use, linked with the goods or services you intend to offer. Be creative and persistent in searching. if you find an obvious conflict, it is probably best to come up with a different word or phrase (if you have been using the word as a trademark for some time, you may have priority over other users, but tis can be a costly road to follow.)
If the Google search reveals no conflict, check with the U.S. Patent and Trademark website at www.uspto.gov. Go to the Trademark section and start with a simple search. Select Search TM Database (TESS), then new user form basic. hit the button for "live" marks, then type in the proposed trademark as a search term and see what comes up. if you get a list of uses, you need to look at the results to see if there is a problem. if you want to try it, I suggest using "Acme", the manufacturer of choice in virtually every Road Runner cartoon. when I did it, 135 records were found. If your use of Acme were unique, there is a good chance you can use it as a trademark.
Hiring an attorney to help with the process is not a necessity, but certainly a good idea.