[JohnG45]

... I cut the contents into small pieces and mail them back in their postage paid envelope.

Why bother cutting up the contents? I just mail back their postage-paid envelope - empty.

(Now that I think about it, maybe you have a better idea. I'm envisioning hundreds of little flecks of paper cascading down on some AARP employee's desk. Or, if the envelope is opened by machine, hundreds of little paper flecks gumming up the works.)

[Eric in the Ozarks]

I cut up the little plastic ID card, too. Sometimes I add in a little extra chopped up newspaper to make a really fat return.

[rcofdayton]

Better yet, wrap up a brick and attach the envelope to it.