To echo some things from above and maybe add:
Phoning a representative is better than a letter, and a letter is better than an email.
Yes, call even the ones who are on your side in a deep (whatever color) state. Why? Remember that everyone who is on your side has things they care about deeply (for example, I care deeply about health care) and things they don’t care much about (for example, I don’t care much about guns). If I were your representative in a deep blue state and you were blue and you cared deeply about guns, you would want to call me up and say “Julie, you ignorant slut, don’t give up something on guns to get something on health care!”
Or say that there is a bill that I might agree to because it gets me something on health care, something not great, but better than nothing. You want me to stand absolutely firm on this issue and let the Rs take the hit. You would want to call and say that. “Do not compromise on this issue. It’s incredibly important!”
I might not listen all of the time, but I will likely listen some of the time.
There are a lot of organizations out there, some big and some small. The tendency for donations is to pick the big guys, but sometimes the small guys are the ones who focus so much on an issue that they have more power. If you really care about X and a big org does XYZ and a small one does X, the small one may be the better bet for a donation.
If you really care about an issue, find where the orgs stand. You can look for things like sign-on letters, etc. and find who is joining together in certain causes (this is also a good way to find small orgs dedicated to specific issues). For example, say you really care about right to die and end of life care. You find sign-on letters about end of life counseling and find big orgs and small signed on. The big orgs maybe care about health care in general, the ACA, Medicare, Medicaid, etc. Among the small orgs, maybe you’ll find one that focuses entirely on right to die. The fact that they are on the letter means they work in coalition, but they are focused on one issue. That might be the right organization to donate to.
And sometimes such orgs can use your help in other ways. Sometimes. Not all organizations are ready to use the help of volunteers.
Social media does impact politics. It’s unclear exactly how much, but facebook and especially Twitter are places where politicos do look to see what people are thinking. Always remember that the vast majority of staffers for federal politicians (I’m assuming this is true at the state level as well) are in their twenties. And remember that the staffers are the people who get things done and are the gatekeepers.
Become knowledgeable. Don’t talk more than you listen. Don’t assume you know the issues just because you care a lot and share the ideology of the people who have strong opinions. Recent events notwithstanding, opinions are not better than facts. Have both.
Be an idealist, but a functional pragmatist. You can talk big but accept small. It’s possible to come back from cuts in programs. It’s next to impossible to come back from fundamental alterations in programs, eliminations, or structural changes. Someone wants to cut some funding for Medicaid? We can accept that. Someone wants to block grant Medicaid? We can’t accept that. Understand how programs work and what changes would mean. If you don’t know the current lay of the land, you can’t know what the changes would mean.
(BTW, I am not an extrovert at all, but I work in health care advocacy and policy.)