My "strategy" is to never sign up for "free magazines", book clubs, CD clubs and the like. Usually they are not interesting at all (in general or compared against the points to be earned) and I don't want to run the risk of forgetting to cancel one of them and being stuck with an expensive and useless magazine, etc. Only exception I make are the (rare) offers where you don't have to give a credit card at signup.

What I will do occasionally are single purchases like books and of course the (in)famous Amtrak and Tupperware offers.

Whenever my point balance reaches a redemption level I redeem my points. You never know what those guys at MyPoints might be up to or do to my account, so I get the points out as soon as I can.