The US Patent Office website is the first place you should start when searching for patents. You can search by keyword, patent number, author, and other ways. I recommend using the quick search to start.
After you have pulled up a patent from a search, find the patent’s U.S. Classification. You can search by classification later to find other patents in the same subject field.
Google Patents is more keyword based. It is easy to use, but beware that sometimes Google Patents may not be as current as the US Patent Office site.
Managed by the World Intellectual Property Organization, PatentScope searches over 30 million patents and patent applications from many different countries.
