Know your issue, do copious background research, and then be succinct, calm, and even in making your point. If you are sitting on the other end of the phone from a staffer, raking them over the coals, for 20 minutes you may feel better, but I can tell you that what you are doing is hurting you, not helping you. As part of a staffer's job is to listen to you, they will, but the second that you start to be disrespectful, they will tune you out. Oh, you'll get a letter, but don't expect the representative or the staff to put in a great amount or time or effort on your issue. Again, treat them as you want to be treated.
If you get to meet with your representative, or their staff, in person -- dress professionally. Do not wear ceremonial robes; cloaks; all black clothing (remember green is the new black!); extreme make-up (or any make-up if you are a male); or wear pentacles the size of hubcaps (this doesn't just go for Pagans, Christians that come in wearing huge crosses get just as little respect).
Many representatives already think that our religious beliefs are part of a cult (mainstream entertainment and media really hasn't helped) and dressing as if you just stepped off of a vampire movie set will just get you laughed at (after you leave) and dumped in the "crazy" file. This also goes for meetings outside the office, such as at town hall meetings and county fairs. If you plan on meeting with your representative, dress appropriately.
Do not attempt to contact legislators other than your own. It is both a waste of your time and their staff's time. By law, only your elected legislator has a "duty" to represent you (and to act on your contact). When we get contacts from people outside the district, we simply forward them to their elected legislator. Since you have probably already contacted your legislator, this just gets you lumped into the "Frequent Flyer" file (for people that seem to have nothing better to do than contact their legislator on any and all issues).
Do not continually contact your legislator or their staff after making the initial contact unless you have something new to share. They already know your position on the issue and if you keep nagging them like a kid wanting a toy, you will just end up annoying them (and getting put into said Frequent Flyer file).
This is a big one -- If your legislator does try to do a bill to help the cause, don't call and attack the bill if you feel that it does not go far enough or if the bill is stuck in a committee. Really good case in point, Mothers Against Drunk Driving came before the Senate Transportation Committee to speak in favor of a bill that would increase penalties on drunk drivers. Instead of giving it their "full" support, the MADD representative spent nearly her entire testimony on how it does not go far enough. Guess what? The bill did not pass out of committee. So, instead of getting something, the state lost and got nothing.
Don't threaten your legislator, or their staff, by saying that you will work for their opponent in the next election, won't vote for them, or will make sure that the entire district knows about this. None of these will motivate your legislator to help you.
Every legislator knows that there will be people working for their opponent, that won't vote for them, and that trying to trash them in the newspaper is often an opportunity for them to make their point to the voting public without having to spend a dime. Threats don't work. They just demean you and your cause -- you might as well threaten to hold your breath, it would be as effective.
This one may be confusing -- Open up your wallet and make a campaign donation -- but don't say, if you vote for this bill, I'll give your campaign money. The subtle difference is that it is perfectly legal to support a politician's campaign, but predicating that support on having them vote a certain way is bribery.
Legislators are more likely to listen to you if you show an interest in keeping them in office. Politicians have to run for office every two, four, or six years to keep their job and every election is more expensive than the previous one. By helping them to buy a few more yard signs or literature pieces will help you get their ear when you need it.
Grassroots movements are great as it is refreshing to see citizens actually getting involved in their own governance. However grassroots moves are only as good as their planning and execution. Sometimes they are effective, and sometimes they do more harm to their cause than good. The sad fact of life is that the everyday citizen's voice is being drowned out by the monied special interests. In order to make your voice heard, through the use of grassroots, get professional help.
Find people who have experience with planning and execution of grassroots movements and enlist their aid in yours. Do your homework on your legislators, find the ones that are, or may be, sympathetic to your issue and try and enlist their support. If the issue is too complex or, more importantly, too important: