I personally have attempted to take up a green life style by riding my bike everywhere instead of my car. I had to force myself to do this by leaving my car at my parent's house while I went away to college. I haven't driven my car in over 3 months now.
I bought fabric shopping bags from a Kroger right down the road and use that for when I shop instead of plastic or paper bags. Paper bags would be my next choice, but I really enjoy my fabric bag!
I have been buying organic foods (so expensive...) but supporting those types of foods is better for the environment.
I find these to be very important principles for taking up a green life style.