I love my dog - he helps me go green:
1) Let your dog clean your plates (literally, or scrape the food into his dog dish). Some restraint is necessary here because a dog that is overfed table scraps can become unhealthy pretty quickly.
2) Cook, and buy, less. I know, I know... this is really hard: "better to have too much than to run out." Hmmm. Maybe, as a society, we eat too much anyway? Dunno. Just puttin' it out there...
3) Compost (this is tricky if you live in an apartment, unless you're really really into plants).
4) Use leftovers. My hubby shakes his head at me for keeping odds and ends in the fridge, but sometimes the next day the kids will eat them. Once they're a few days old then I either let pooch or the trash can have 'em. At least this way they've had a shot at being used, rather than just being discarded.
5) Freeze what you can. I was habitually buying too much fruit and seeing some of it spoil until it occurred to me that I could freeze some to use in smoothies.
(My dog is shaking his head at me... he thinks items 2 through 5 are silly...)