You can begin your search the following way:
1. Brainstorm keywords to describe your invention, such as synonyms.
2. Use your keywords to search for a similar match of your invention in Google Patents. The advanced search lets you enter phrases, exclude words, etc.
3. If you find a similar invention, write down its class and subclass.
4. Use the class and subclass to search patents and patent applications with the USPTO website classification search. The USPTO website is more current than Google Patents.
[Note: The default search is CPC (Cooperative Patent Classification), which harmonizes the former European Classification (ECLA) and United States Patent Classification (USPC) systems.]
5. Trace related patents through references.
See our guide to Intellectual Property and Patents.