Be courteous and respectful in all communications. If a bill deals with a problem but seems to represent the wrong solution, propose constructive alternatives. Take a position. Ask your representatives to state their positions on the issue in their replies. Avoid stereotyped phrases and sentences that give the appearance of form letters.
Personal communications are more effective.
Time your letter to arrive when the bill is in committee, before it is approved and sent to the floor for a final vote. Write when the legislator does something of which you approve. A word of appreciation will create a more favorable light for the next communication. It's good politics. Members know your vote can be won or lost by their response.