You cannot use a brand in commerce if your use would be confusingly similar to someone else’s brand. So, do not name your company or your product or service without clearing trademark rights first. Once you choose your name, scour the internet using the search engine of your choice to ensure no one else is using it as the brand name of similar goods or services. Also check the TESS trademark database at uspto.gov to see if your name turns up. Remember that trademarks are compared on the basis of their overall visual and phonetic impression, so clever spelling inconsistencies – substituting a Z for an S, for example – should be ignored in this process.
If you cannot find your name in use anywhere else as the brand of similar products, go ahead just in case and have a formal trademark search conducted by a competent trademark lawyer, who can tell you whether you will be able to get a trademark on your brand and, perhaps more importantly, whether someone else is going to sue you if you start using it.
Then, and only then, is it safe to start naming your company and branding your products with the name that passes through the above clearance process. Remember Trademark rights are obtained neither by forming your corporation or LLC at the secretary of state’s office, nor by registering a domain name. Those ministerial items, while important, do not matter to the trademark process and should come after trademark rights are clear.