1) Plant trees or save trees: Think green. Saving trees will also help save wildlife.
The destruction of trees is the primary cause that global warming is taking place today. So if you can just plant as many trees as you can and ENSURE that they survive; you are doing your two bit worth. If you cannot plant trees, just make sure you can save trees from being cut down, or drying up and dying due to lack of water. Make it a point to water at least one tree or plant in a day, in your yard, garden or neighborhood.
2) Save paper: avoid taking unnecessary printouts. Use recycled paper. On a lighter note: Teachers, give your students less written work. Instead of getting each student to buy their own text books, the school can provide text books on a borrow-able basis as in a library. This will save the students of carrying horrendous loads of books to school and back- especially true for countries like India where student's daily school bag weighs a ton with the amount of things some schools insist they carry!
3) Limit the use of air-conditioners- build up your tolerance levels and get used to living in natural whether and climatic conditions.
4) Stop using deodorant and aerosol sprays. Air conditioners, refrigerators and aerosol sprays use CFC or cholo-fluro-carbons. When CFC leaks into the atmosphere, it does deplete the ozone in the air. The Ozone layer is what protects us for harmful radiations of the sun.
5) Builders and architects should use less glass on outer walls of buildings in their designs. For example- a tall building with a glass façade from top to bottom will heat up in the summer. The amount of heat generated is just added to the already hot atmosphere on the outside of the building,