How can individual citizens change laws?

From a common law perspective, since there are no actual laws written out, it is my understanding that all decisions are based on precedent. Therefore, the only way to change the law would be to change the precedent right? In that case, is it true that the only way to change the law would be to bring a new case in front of the court and have the decision change the precedent? In other words, individual citizens don't really have power to change laws here, do they?

From a civil/criminal law perspective, do cases depend strictly on the criminal code or do they depend on the criminal code as well as precedent? Is it just the criminal code and than the judge interprets it and uses common sense based on the situation? How can the civil/criminal law be changed? Is there anything individuals can do to change the criminal code, other than simply raising awareness of an issue in hopes that the government will take notice and amend the criminal code?

Yes, what I'm asking is specifically how an individual would go about changing a law THROUGH THE GOVERNMENTAL PROCESS. If an individual spots a law that they think is completely immoral, how do they go about getting the government to change it? Is that the only option? To convince the government (as opposed to, let's say, doing it in court?)

And so the only way of doing that, really, would be protesting, writing letters to senators, signing petitions, etc? Am I right about this? And I supposed voting for the political party that espouses your beliefs. That's all the power an individual really has, right?