Search for all keywords related to your domain in Google and review the top ten results.
You should spend 10 to 15 minutes on EVERY keyword that you use in Google.
Delete keywords that have many authoritative sites on the first page.
Good things to find are:
If you find a lot of these types of results, chances are you'll be able to distance them.
Make sure the keyword you choose contains enough research per month to justify the work. Also make sure the research intent will convert them into profit.