It's a war. The spammers WANT to send you their crap, so they don't offer you an easy way to get rid of them. Moreover, they sell and share email lists with other spammers.
There is no Do Not Spam signup the way there is for Do Not Call. There has been talk of doing this, but enforcement would be difficult without more regulation of the Internet.
Legitimate spam (marketers who are trying to foist their products on you but not to actually con you) offer an opt out link, usually in small print at the bottom of their email. Beware of giving them any info other than the email address to which they are no longer to send their email. Many will then send you another email to confirm that you really don't want their spam. Then when you confirm it, they will send you another email to say it'll take ten days to process your request. And they may blast you with spam during that time (and we all know the request can be process instantly, automatically).
So the best way to avoid it is prevention.
1. Keep your personal email private. Make sure those people who have it know not to share your email with others. tell them not to put you on group emails for jokes, sayings etc, because those get shared with other people, who share them with others, and meanwhile, your address is there for all to see and it doesn't take long for a spammer to grab it.
2. Keep a separate email address for vendors, because even the ones you want to deal with will pass on your info. Buying online? Staying at a hotel and want reward points? Want to give your email to a local business? Give the vendor address.
3. Use a separate email for email groups. Same idea, and it also keeps your main address from clogging with posts from an active group.