Maintain at least two email addresses. Use your private address only for personal correspondence, and another address for registering on public forums, in chat rooms, to subscribe to mailing lists etc.
Your private address should be difficult to guess. Spammers use combinations of obvious names, words and numbers to build lists of possible addresses. Your private address should not simply be your first and last name. Be creative and personalize your email address.
Treat your public address as a temporary one. The chances are high that spammers will get hold of your public address fairly quickly if it is frequently being used on the internet. Don't be afraid to change it often.
Never respond to spam. Most spammers verify receipt and log responses. The more you respond, the more spam you will receive.
Do not click on 'unsubscribe' links in emails from questionable sources. Spammers send fake unsubscribe letters in an attempt to collect active email addresses. If you click 'unsubscribe' in one of these letters, it will simply increase the amount of spam you receive.
Never publish your private address on publicly accessible resources.
If you must publish your private address electronically, mask it to avoid having it picked up by spammers. ‘Joe.Smith@example.org’ is easy to find, as is ‘J.Smith@example.org’. Try writing ‘Joe-dot-Smith-at-example.com’ instead. If you need to publish your private address on a website, do this as a graphics file rather than as a link.
Consider using a number of public addresses in order to trace which services are selling your address to spammers.
Make sure that you use the latest version of your web browser and that any security patches have been applied.
Use an anti-spam solution and only open email accounts with providers who provide spam filtering.
If your private address is discovered by spammers - change it. This can be inconvenient, but changing your email address does help you avoid spam - at least for a while!