Spammers use automated tools to harvest e-mail addresses. Make it difficult for them. Whenever you give out your e-mail address in a public forum - such as a newsgroup, mask it so that only a human can understand it. For example, if your e-mail address is joe@mytown.com, enter it in the newsgroup as joemytown.com.
Computer programmes that troll for e-mail addresses are not smart enough to recognise this as a standard e-mail address.