To qualify for federal trademark registration, marks must be sufficiently distinctive and not infringe on any existing marks. To determine if your mark has already been registered or if there are other uses that may impede registration of your mark, a comprehensive trademark search is highly recommended.
As for trademark distinctiveness, there are several possible categories, from most distinctive to least: fanciful or arbitrary, suggestive, descriptive, and generic.
Your mark also may not be offensive or disparaging, merely geographically descriptive, primarily function as a surname, merely descriptive or generic for the goods/services offered.