Advanced negative keyword match types allow you to further refine and exclude irrelevant traffic and get only the most relevant clicks. Negative match options include broad, phrase, and exact match.
Review your search terms reports to see what searches are triggering your ads. This is one of the best sources of new negative keywords with data specific to your account.
If you are in the planning stages of your keyword lists, use Google's keyword tool to research keywords and note any words or phrases that are irrelevant.
To add negative keywords, follow these steps: