Whether you are supporting or opposing a piece of legislation, clear reasonable expressions of your opinion will get priority treatment on the Hill. Avoid excessive documentation. It won't be read. Try to make your point in one or two pages. A piece of legislation can go through as many as 25 steps before it becomes fully operative.
Legislation begins in a congressional subcommittee or a full committee.
The time to contact members of a committee is when legislation is about to come before that committee. Another key time occurs when a bill is about to come before the full Senate or House. You should contact both your senators if it is a Senate bill, and your representative if it is a House bill. To obtain a copy of a bill, contact your representative or senator's district office. The first without the second is meaningless.