Query Mining- Not all searchers are created equal, depending on location, regional dialect, education level, familiarity with your product/industry there is a good chance that many queries or search terms will direct visitors to your site. Broad match can work like a net and capture multiple variations of the keyword set on broad match and extend your reach to potential customers.  It is quite possible there are potential customers searching for your product or service but are using search terms that you may have not thought of.

Fortunately, many paid search tools show the query that matched up to your advertisement. By keeping an eye on the amount of times certain variations show up you can take some of these queries and turn them into Exact match keywords. This should lead to cost savings and a potential higher quality score.

Use Negative Keywords-  As mentioned above, Google will match your broad match keyword to a wide array of queries they consider relevant. By using negative keywords you can insure that your ads will only show up to relevant search queries by blocking certain terms.

For example, if you are selling bonds, you may have the term "Bonds" set on broad match. Google may attempt to match this broad match keyword with search queries such as "James Bond" or "Bondage" which are obviously not relevant to your website. By setting terms like "James Bond" and "Bondage" as negative keywords you guarantee that your ad will not be broad matched to these terms.

Create Relevant Ads and Small Ad Groups- With Google matching your keyword to a large array of search queries chances are you may end up showing an irrelevant ad to a potential customer. By keeping small ad groups and creating as targeted text ads as possible you stand the best chance of presenting a relevant ad to a potential customer.

Overall broad matched should not be overused - it can drive inferior traffic to your site at a premium price. Using it sparingly and utilizing it as a keyword research or query mining tool is a best practice that provides optimization to your account.