SPAMmers are very shady when it comes to collecting your e-mail addresses anymore. Whereas they used to just buy lists of e-mail addresses from sites that would sell them, now they harvest them.
- Be very careful about what sites you send your address to. Most legit sites will explicitly state that they will not sell your address. If they don't state this, it's anybody's guess as to whether or not it'll end up on some SPAMmers list.
- Never click unsubscribe to any SPAM that you know isn't from a legit source! I cannot stress this enough. If you get an e-mail from CNet or whatnot, then go ahead, BUT if you receive one about 'enhancing' certain parts of you that you don't usually have out in the open, then clicking the unsubscribe like will only VERIFY for them that the account is active. You won't stop getting the SPAM, you'll get MORE.
- Don't post your e-mail in any readable format on a forum or blog. SPAMmers have webcrawlers just like the search engines do. The difference is, these harvest the e-mail addresses on the pages and add them to their lists. If you do post your e-mail on a blog or whatnot, then use a format like this: username <at> wherever dot net. I imagine that the more intelligent crawlers will even get that, but at least most of them will not pick it up like they would username@wherever.net.
- Have a separate e-mail account. I have an account specifically set aside for SPAM. I give it to websites and the like. They usually have mailing lists of their own, and some, as stated above, will sell you out.
- Some trojans on people's machines also harvest the addresses out of their address book. In this case, there isn't much that you can do, since your friends are likely to have you in their book. Spyware removal is definitely a major way to cut down on your, and your address book's SPAM. So, if you buddy has some spyware on his system, have him use a spyware removal tool, then change your e-mail address. Filters are great and all, but they don't stop everything, and often stop what they shouldn't.