Before beginning the trademark registration process, the individual or organisation must conduct a trademark search in the trademark database. Before you apply, you should search the USPTO's trademark database to see if any trademark has already been registered or applied for that is similar to your trademark, used on related products or for related service. A trademark search will provide information about identical or similar trademark that already exists and has been registered with the registry.
If it is already registered, the same mark cannot be taken through registration process as a trademark that meets such criteria will prevent your trademark from being registered because it creates a likelihood of confusion.
A trademark search can be conducted by visiting the Trademark Registrar Website or by seeking assistance of professionals in the legal field who are experts in the same. It is a very essential step to be taken before starting with any kind of registration process so that at later stages there is no delay or rejection of your application.