Get some of your other colleagues to call as well. Several well-informed phone calls from constituents are impressive. Find out after a vote is taken just how your legislator voted, and follow up with a thank you note, or a polite I was disappointed to see note. Ask for a meeting. It is fine to bring along one or two colleagues, but rehearse your points ahead of time.
Nothing reinforces a position better than a real life or local example.
Be a good listener. Ask for advice. Be candid, and if you don't know an answer, get back to your legislator promptly with the information. Don't be afraid to show passion about your issue, but always be courteous and non-threatening. Never promise support or a contribution in return for a vote.