Don't respond to spam. Some spam messages contain links that promise to remove your email address from a mailing list. However, when you select these links, you prove that your email address works, and the person who sent the message could sell your email address to other spammers.
In addition, read the web site's privacy policy before you provide any personal information. Most web sites explain their policies about how they use your personal information. If a Web site doesn't have a privacy policy or if the privacy policy doesn't explicitly guarantee that your personal information will not be shared, there is a possibility that any information you provide to that site could be sold to spammers or other direct marketers.
You can further reduce the amount of spam in your personal inbox by restricting the use of your personal email address to correspondence with people you know. All other correspondence, such as on-line purchases, should be done using a sub-account. Verizon offers an on-line Flash tutorial for creating sub-accounts and configuring Microsoft Outlook Express.