Patent searches are done using keywords to describe the invention. However, they can be tricky because they often use technical jargon that you may not think of: in fact, sometimes inventors purposefully describe their inventions with confusing wording to make the patents more difficult to find.
Imagine that you want to search for the Koosh ball. You cannot search by the name "Koosh ball" because
1. the product name isn't part of the patent
2. patents using the term "Koosh ball" will be based off the original invention, but won't be the original invention.
You need to think of words the inventor would have used to describe the ball in order to find the patent. Try something like:
(sphere OR ball) AND (rubber OR elastic) AND filament
The patented description of a Koosh ball includes many of these words, so this is an excellent search.
Patents are assigned classfication numbers, usually in several categories.
One classification code for the Koosh ball is A63F9/0278, which is the code for human necessities → health; amusement → games → projectiles. The Koosh ball also has several other classification codes assigned to it. Searching for classification codes is a very effective way of finding similar patents.
Find out more by working through the University of Maine's 6.5-Step US Patent Search Strategy Guide.
Like article searches: Look through all the results, even if they seem irrelevant. Patent titles aren't usually accurate descriptions of the document contents. Be thorough so you don't miss anything! Your ability to generate synonyms and alternate descriptions can make or break the search.
Unlike article searches: In a patentability search you are trying or hoping to prove that there are no inventions close to yours. You have to be sure that you are not getting anything because nothing is there, rather than because you are not asking the right questions.
It is always important to document your strategies during research, but it is especially important to do so when patent searching because of the potential legal ramifications. If there is any sort of legal aspect to what you are doing you may be called upon to explain what you did and when.