A preliminary step to reducing is knowing how much you are currently using (or with regard to carbon emissions, producing). Carbon footprint calculators estimate how much carbon your life produces and sends into the atmosphere per year.
The Nature Conservancy provides one such carbon calculator: Carbon Footprint Calculator - What's My Carbon Footprint ? By using it, you will get an idea of what kinds of activities contribute to carbon emissions, how much each activity adds, what your overall footprint is, and how you might reduce it. Along with providing this information, the carbon calculator gives you a baseline from which to start whittling away at your footprint. Because it gives me something to shoot for, I find knowing my footprint to be energizing and inspiring. As the footprint decreases because of lifestyle changes I make, I feel empowered to address global warming.