No plastic or paper!
One of the eco-friendly things I've started doing when I shop in multiple stores (like a mall) is to use my existing bags rather than a new one from each store. If I have a best buy bag with a dvd in it, I stick my cat toys in that bag rather than getting another one.
We try to keep the plastic bags at the house for other uses rather than throwing them away – after a while, they can really pile up. Reusing the bags I'm already ... uh... using has helped combat this clutter.