Here's a quick tip to elude a few of the techniques spammers use to figure out which of the email address on their lists are valid, and to perpetrate other mischief: turn off execution of scripts and showing of remotely loaded images (or all images) in your email client. Either can alert spammers of the fact that your read their mail, and maybe even how long you spent looking at it, which validates your email address and encourages them to send to you again.

To turn of images in MacOS X's built in Mail client, select "Preferences" from the "Mail" menu, click "Viewing", and deselect the "Display images and embedded objects in HTML messages" checkbox. Similar settings and settings for scripting can be found in other email clients...somewhere. Look in the preferences panel--it shouldn't be too hard to find.