I do small things, and try to teach the boys to do small things too.
Whenever we go for a walk or to a park, we bring a shopping bag, and pick up any trash we find laying around.
I have taught the boys not to let water run while brushing teeth or washing up, and we bathe them together.
We recently had to replace our washer and dryer and we opted for the more efficient front-loading kind.
We turn lights and appliances off when we leave rooms. (exception is at night we leave the bathroom light on for the boys - they're a little afraid of the dark) Of course we had to learn to do this because if you have too many things running in our house at once, the power goes out. And I won't go in our basement when it's dark so if the power goes out while he's not home, it stays out til he gets home.
We keep our thermostat low and dress warmly/use blankets at home.
Right now we are not shopping for a car but we will be at some point in the near future. If Thing 3 is in our future, we will need a minivan (our Saturn won't hold 3 car seats). That will replace my old 1991 clunker. When the time comes to replace the Saturn, we will get a hybrid.
I try to clean with environmentally friendly products. Baking soda, vinegar, and the Method line of products are what we usually use. (I do use bleach and harsher cleansers when needed but I've cut back quite a bit on them)
There is still a lot more waste going on in my life than I would like, but we are making small improvements as we can.