1. When the telemarketer calls, don't hang up the phone on them. Ask if they can hold for a moment. Then, place the phone down and walk away. When you hear it beeping, hang it up. Consider it a public service. While they are waiting for you, they aren't bugging anyone else.
2. When you get those pre approved letters in the mail for everything from credit cards to 2nd mortgages and junk like that, most of them come with postage paid return envelopes. Get rid of some of your other junk mail by putting it in these envelopes. Send an ad for your local chimney cleaner to American Express. Send the pizza coupon to Citibank. Or... just send the application back and leave everything blank.