Adding negative keywords to your account is one of the best methods you have at your disposal to improve your Quality Scores and weed out irrelevant clicks. A good list of negative keywords will ensure you are not paying for traffic that you already know will not convert to sales and leads.
You'll need to do some research to generate a thorough list of negative keywords. Part of this process is using your common sense and thinking of potential related queries that will not be relevant. Aside from brainstorming potential negatives, you can also use the following tools: