Separating trash, throwing nothing into the environment, driving a low consumption car. Can't say I'm a vegetarian, but I always buy the most expensive meat (I can afford) because of the better living conditions for animals.
Basically I think everybody should do the little things they are capable of / can afford. If everybody did that, we'd already be living in a better place.
And then I try my best to understand things and inform others. Because one thing the environmentalists do these days is waste an incredible amount of money without even thinking twice if they couldn't be doing a lot more with a lot less if they just position the lever in a better place. One such example would be germany's promotion of electric cars. Electric cars are not even that good for the environment, they are good for the german economy mostly, which is not a bad thing either I suppose. However they should just have invested into the railroad system (which basically sucks) and would have resulted in getting most of the trucks from the Autobahn and made germany a cleaner and healthier place, quite a while ago...