A trademark search, or “trademark clearance search,” is a form of brand due diligence and is a very-advisable activity prior to finalizing branding strategy or beginning the federal trademark application process. While distinguishing your brand from that of your competition is generally a good thing, whether your brand’s marks are sufficiently distinct to qualify them for federal trademark registration is a narrower question.
The initial analysis is whether your proposed mark is inherently protectable; e.g., it is not commonly descriptive /generic or mis-descriptive. Subsequent analysis is the trademark search itself, preempting what the trademark examiner will do once your trademark application is filed: namely, determine that there are no live registrations or applications for registration with which registering your mark would create a likelihood of confusion.
In addition to uncovering potential conflicts within the USPTO, it is prudent to more-broadly survey the market landscape for potential uses which may become problematic through oppositions or upon geographic expansion. The following flowchart outlines a very basic process from mark conception to application.