It seems like "Global Warming!" is the usual green battle cry, but I think that is the wrong road to take.
For one thing, whether it should be or not, global warming remains "controversial." A small handful of "scientists" deny that it is happening, and they get lots of conservative media coverage. Up until very recently, the president has denied that there is any problem. My dad continues to insist that global warming is a big lie.
And while most people believe in global warming, "a majority of Americans don't believe global warming will pose a threat to them in their lifetimes."
I think that rather than trying to talk about global warming, we should stick to things like air pollution and water pollution, which are what ultimately is causing the global warming anyway. As you can see on the chart above, global warming is near the bottom of the environmental concerns list. And *no one* is going to argue about whether or not clean air is a good thing. My dad, on the other hand, will turn blue in the face telling you about the myth of global warming.
Another problem with global warming is that it's such a huge problem. It's easy to feel like "I'm just one person. How can I have an impact on global warming?" That's happening on a bloody global scale! Air pollution is a much more localized issue. I shouldn't have weekly bonfires just for the heck of it, because it affects my local air quality. If my city gets a public transportation or carpool initiative going, that affects my local air quality. If another coal power plant is built (say it with me now!) that affects my local air quality!
Another plus of talking about air and water quality- it's much easier to deal with those issues on the small scale. Turn off lights to save power to reduce air pollution. Turn off the tap while brushing teeth to save water to help preserve water quality. These small steps can turn into bigger steps as the individual adapts. It makes dealing with environmental issues manageable, rather than trying to think "what on earth can I do to help with global warming?", panicking, and then doing nothing...