I find the following seems to work to varying degrees:
1. Write, e-mail, and call them, let them know what you think and what you want them to do. Do this even when you agree with their stance on an issue, they need the pat on the head just like a dog. When writing to them don't be a partisan hack and name call (I have responded to a rather patronizing letter from one of my senators like that but never with the initial contact on an issue)
2. Show up at one of their town hall meetings (my stupid rep to the US House like to have phone ones) and ask hard questions on the topics you care about framed to make them look bad if they don't answer in the way you want.
3. When their supporters or they themselves are out door knocking during the campaign season have a list of issues you think they screwed up on and why and thus will not be voting for them. Also mention that you have informed you neighbors about it and actually do so ensuring that they hear the same issues several times.
4. Write letters to the editor in you local paper calling out their action or lack of action.
5. Become active in their campaign (or that of their opponent) and in the local political machine so you can help direct the platform and their thinking.
Granted all of that does require putting in some effort instead of being a simple voter, but does seem to garner reasonable results.