If you know a way to make the world a better place, do it, and teach others how to do it, spread the word!
Protect the weak, speak for those who can't speak for themselves, fight for those who can't fight for themselves.
Do not litter. Recycle instead.
It is always good to do someone a favor. Never be afraid to help someone out.
Volunteer to be a reading tutor at your local grade school. Just being nice to kids teaches them to be nice to others.
Start a big garden with all the compost you made, and grow food so that you don't have to go out and buy it.
Don't waste food. It's better to buy an average amount and eat it instead of over-buying and in the end up tossing away the leftovers.
Make sure you inform mostly everyone you know about pollution, and especially global warming. We do have the freedom of speech, so go stand up on a big rock and tell the world how to help, stating the steps above in your "surprise speech".
Donate money to charities, whether they are big or small. Not only do big charities need money, but small charities need it a lot. An example is animal inc, a charity that sells baked goods and other products to reduce animal abuse.
Going vegetarian doesn't just help animals! It reduces the amount of carbon emissions put out (helps with global warming and the environment), allows more food to be made for the hungry, and even reduces your risk of cancer (not to mention heart disease and obesity)!