Doing the search yourself
If you already understand how trademark registration works, an online trademark search tool may be all you need. If you don't, it's wise to bring in a trademark attorney or a service such as Marcaria.com to handle your registration, particularly the search itself. The process can be complicated and slow.
Why the search matters so much
A trademark application that isn't completed correctly can be held up for several months, and it may cost you more than you planned. The trademark search is one of the most important steps along the way.
A comprehensive search is essential in today's market because there are more and more unregistered and common law trademarks. Globalization adds another layer: you need to think about international markets and register your trademark in other countries to protect your brand and your property rights.
What a search cannot promise
Even a very thorough search does not guarantee that your trademark will be accepted and registered. For that, consider a Trademark Study, which is an in-depth review that also includes a formal assessment of how likely your application is to succeed.