You don't have to do the data collection yourself. You can buy and customize lists to suit your specific needs--for example, to target healthcare professionals earning more than $100,000.

Dun & Bradstreet's is perhaps the best-known source, with over 85 million individuals in its database; also using the Dun & Bradstreet data is . Yet another source of CRM prospects is , a member of Infogroup.

However, such lists are not without fault, even when purchased at a premium. You can expect to find some "bounces" even on the best of these services as people change jobs (or at least change their e-mail addresses). Perhaps up to 10 percent of the entries may be "bad," so plan accordingly.

As mentioned above, the terms of service for most social networks prohibit commercial use of the information contained in their sites. It might seem easy to obtain e-mail addresses from members of a particular social network, but this action violates the terms of service for most networks. Basically, you can use your fan page and solicit contacts by asking them to be your friend or to join your network, but you can't copy someone's information without their permission.