The US Congress considers several hundred bills each session. Senators and Representatives depend upon staffers and, unfortunately, high-paid corporate lobbyists to dissect the bills, offer summaries, and provide advice. Progressive Democrats of America (PDA) launched the Educate Congress campaign to involve ordinary voters in this often overly complicated and undemocratic legislative process.
There are a number of ways that you can contact your Congressional representatives; you can email, call or pay a personal visit to their district or DC office. The action that consistently gets the most attention is stopping in at an office and dropping off a letter outlining what you'd like the office to consider.
MoveOn.org Petition - Congress Don't Renew Fast Track
Public Citizen Petition - Congress Must Reject Fast Track Authority
MoveOn.org Petition - Stop the Trans Pacific Partnership
CREDO Petition - Stop the Massive Corporate Power Grab