You may want to use more than one method to discover competitors, as none of these is complete or foolproof. Some types of businesses such as consulting businesses or manufacturing operations might need additional sources.
The D&B Million Dollar Directory will work to find U.S. based competitors for most types of businesses. It is also one of the few places to find self-reported sales figures or estimated sales figures for small private companies (although often still inaccurate, these sales numbers are usually better than those from other sources).
The advanced search allows you to create lists of companies by many criteria, but it is a little tricky to use. Here is an example search
1. Choose Advanced Search
2. First we establish search criteria, then we execute the search. We want to find a list of companies in your industry that are located in Ypsilanti MI.
Choose location criteria from left menu.
3. You will have to navigate difficult menus till you have been able to add Ypsilanti MI to Criteria.
4. Note that the criteria will get listed in the yellow box for current criteria.
5. Repeat steps 2-4 to add the industry to the criteria. (use Industry instead of location)
6. When both criteria are set up, Run Search.
7. This should generate a list of companies. The list could be more than one "page" long.
8. Clicking the company name will get you more information on the company.