• Use any fil­ters your ISP or email provider have in place
    Ask your ISP or online ser­vice if they pro­vide any fil­ter­ing, and if they do then take advan­tage of it. If it’s impor­tant enough to you, and they don’t pro­vide that ser­vice, either switch or put pres­sure on them to add that fea­ture.

    AOL users can enable fil­ter­ing by chang­ing their pref­er­ences some­where online—under Mar­ket­ing Pref­er­ences, I think, but it’s been a long time since I used AOL (and they didn’t offer those fil­ters back then).

    Hot­mail and some of the oth­er web-based email ser­vices also offer spam fil­ter­ing now, although I don’t know how well they work. GMail’s fil­ters are quite effi­cient, so much so that I don’t think I’ve ever received spam in that account. I have learned to check for valid mes­sages marked as spam, though.
    Caveat: if your ISP or oth­er ser­vice uses a “chal­lenge and response” (C/R) sys­tem to avoid unwant­ed mes­sages, please don’t use it. C/R sys­tems are bro­ken, and make it much less like­ly that you’ll actu­al­ly hear from legit­i­mate con­tacts. This arti­cle offers a good sum­ma­ry of the prob­lems with C/R spam fil­ter­ing.

    Use the fil­ters in your email pro­gram. Most of the com­mon­ly-used pro­grams, like Thun­der­bird, Out­look, Eudo­ra and Pega­sus, can fil­ter your mail for you now. Check cnet’s Download.com if your cur­rent email pro­gram doesn’t have fil­ters built in. Even though I get hun­dreds of mes­sages a day, it’s always easy to spot any­thing unwant­ed that gets that far right away—the spam stays in the in-box, and all the expect­ed email is fil­tered to fold­ers for lists, newslet­ters, cor­re­spon­dents, etc.

    If you run your own mail serv­er, you can use proc­mail or Spam Assas­sin or oth­er tooks to set up fil­ters at the serv­er lev­el.

    Then there’s the not-free—but not expensive—service, Spam­Cop. They catch almost all the spam, and you can set up your own whitelist and black­list of address­es in addi­tion to their fil­ters. I’ve been using their ser­vice for many years now, and I love it. If you’re on a lot of mail­ing lists, though, you’ll prob­a­bly want to set up a sep­a­rate account for those that doesn’t go through Spam­Cop. They make it very easy to report any spam that does get through (on that or any of your oth­er address­es), which serves to improve their fil­ters.