The Federal Trade Commission's national Do Not Call Registry went into effect October 2003 (and many states have their own registries). Anyone soliciting by phone should be aware of the rules: Even if a person is on the DNC list, you may call if you have already established a business relationship; you have been given prior written consent; or your call is not commercial and does not include unsolicited advertisements. Violations can bring fines up to $11,000 per complaint.

Businesses are required by federal law to scrub their contact list against the DNC registry every 31 days, which could mean downloading and checking millions of names and numbers. That takes a lot of time. Authtel Inc. has developed, a Web-based service to help you check phone numbers against the national and state DNC databases. It's updated daily and you can set up an in-house list of numbers to avoid. In recent years, several home improvement companies have been caught by the FTC. Even if you're a small company, you can't hope to fly under the radar on this.