Here's another idea from a reader at www.gohlkusmaximus.com:
I'm a dork. I save plastic grocery bags because there's no reason to get a new one every time I go to the store—it's wasteful. However, every time I go to the store, I forget to grab one from my drawer of many bags. When I come home, I add the new bag or three to the already full drawer. How can I stop this repetitive pattern of destructive behavior?
The solution is simple. I designed a visually stark but effective [and clever] sign to tape to the back of my door. Now, when I leave for the store, I'll be reminded not only that I need to go back and get a plastic bag, but also that I'm a dork.
Click here to get to his site, or to download his cleaver sign.