Call them. Write to them. Write to your local papers and other news outlets. Donate to and work for appropriate other outlets, such as FR (IOW, Freep them). Get involved in political organizations or, if there aren't any that advance the cause (as you see it) start one.
Marsha Blackburn is my congresswoman and I've contacted her office several times and am very pleased with her responsiveness. Harold Ford's district is next door and I've contacted him several times and he (surprisingly) listens as well. It doesn't usually have a major affect, but it does sometimes.
You have a specific topic or target you want to influence post a specific question on FR (maybe even start a thread each time) soliciting advice. You'll likely get more than you can possibly act on and some of them will even be easy and effective.
The FR community is one of the greatest resources we could possibly have.