In terms of participation in the governance of our civil society, voting is just the beginning of our civic responsibility. Admittedly for most people, it is seen as the end of their responsibility. For good or ill, what this means is that those who choose to be more active than just voting actually have more influence over policies and governmental actions than their mere numbers would suggest. Furthermore, in practice the people in office only hear directly from a very few of the people they represent. Therefore, those who make the effort to communicate with them can do much to inform them about non-obvious aspects of different issues.
Our representatives do hear from lobbyists and other folks who earn their living working to influence policies in one direction or another. But, in the final analysis, representatives want to win elections. And they judge what their electorate expects by the information that comes to them from their electorate. Every elected official has a good place to which to send email than will be read.
Representatives are hungry for good data and information. If you have some expertise in a given area, offer yourself as a resource in that area and be prepared to be called upon. What better way to influence policy is there?
To do their work, every representative's office has people that specialize on particular issue. If your information is useful, there is a pretty good chance you could establish a working relationship with the appropriate members of the staff. When a question or concern comes up, "Who are they gonna call?" You don't necessarily have to wait for their email sorting process to filter your letter to the specialist. You can ask the office who their specialist on a particular topic actually is and communicate with them directly. Those staff folks work under lots of pressure and really value having a go-to person on their list.
Sadly under current law, elected officials need to spend 60% of their time fundraising. Contributions count. It's always helpful to add a note explaining what actions of the officials lead you to want to support them.
Voting is important. But you actually to get to "vote" more often if you are active in communicating with your elected officials. Figure out a way to build a relationship with them or with members of their staff and your view on your favorite issue gets a bigger hearing.