One tiny little thing I do to help prevent needless waste is to carry a food storage container (i.e., Tupperware) in my purse. That why went I can’t finish my meal, I don’t have to ask for a disposable take-home box.
Think how many plastic or styrofoam containers a person uses in a year… those containers will stick around in the landfill for centuries.
This method is painless and guilt-free.
So, why not stow a small container in your bag right now?
The one in my purse has a reusable shopping bag inside (the black one shown is a slingsax by Envirosax, I found my first one here in Dublin in March 2010). That keeps things in my purse as compact as possible.