Visit the United States Patent and Trademark Office website and navigate to the Patent Attorney/Agent Search page. This federal agency is the legal authority for the registration of patents and keeps a current list of all agents licensed to practice before the USPTO. You can search by name, business name, city, state, zip code, or registration number. You may also use the updated lists which give registered agents by state.
Find a patent agent in your vicinity and call any you've selected to screen them for experience and qualifications. Describe your invention in general terms without getting into specific information about design or mechanics. Ask about recent patent applications they've seen through to approval and those they have had difficulty with. Ask about their areas of expertise and when they passed the U.S. patent bar examination. Ask how they charge for their services: fees, costs, travel expenses, and the like.
Search the Internet for any consumer complaints lodged with bona fide state or federal agencies against patent agents you've screened. Typically, secretary of state offices have consumer protection divisions. If the agent is a licensed attorney, search your state's bar association website for any complaints or charges against your prospects. Read through your prospects' websites and any literature they provide for information on success rates, past cases, and an explanation of the patent-application process.
Sign a fee agreement with the patent agent after carefully reviewing it. This step should be taken before you file any applications with the USPTO, although patent agents will be able to assist you if the process has already begun. Provide more detailed explanation of your patent idea, as well as drawings and specifications, only after you've signed the retainer.