You can work to persuade politicians to pass or oppose laws.
Know your subject. Politicians hear opinions from all sides on an issue. If you only know a little, you won't get far.
Learn the rules. What does it take to get a bill voted on? Ask an assistant how the legislative process works.
Find allies. What organizations have the same interests as you? Convince them that you can help each other by lobbying together. Find other politicians who will support your cause.
Know the opposition. Learn their arguments. You'll have to overcome them.
Don't burn your bridges. The saying, "Politics makes strange bedfellows," means that you might sometime need the support of someone you on occasion may consider an opponent. Don't ever take part in personal attacks. Stick to the issues.