Things you can do:
1. Find an energy provider who sells green energy - here in Germany, it's possible (and common) to buy 100% green energy, but I don't know what it's like where you are. Even if it costs more, get the green energy - it's a big change you can make that won't affect your lifestyle one bit.
2. Reduce the amount of red meat you eat. The environmental costs of this are well known. Give it up if you can, but if not, at least reduce it.
3. See if you can fly less. If you fly intercontinenally, then the CO2 from that will dwarf almost anything else you do. Again, this is something that's easy to say, but it's something that's very effective.
Those are the changes you can make in your personal life. There are plenty of other good suggestions here as to how to make systemic changes.