You can tell your computer to forget you were there. Participating in online chats or bulletin boards can often reveal your e-mail address to others, whether or not you want to be contacted.
Hackers know common names people use.
Always use a combination of numbers and words you can't find in the dictionary. It's also a good idea to change your password on a regular basis and avoid storing it near your computer. If you want to receive only certain catalogs, contact the organizations sending you the ones you don't want and ask to be taken off their mailing lists. If you're not online, you can also call the DMA at 212.790.1488. You can give your Social Security number more security by not writing it on the back of a check.