The Project on Government Oversight (POGO) recently published a new handbook outlining "best practices" for congressional oversight of government. It's available free to members of Congress and their staff members. If you are not a denizen of the Hill, you can buy it online.
I'll give you the bottom line for free: don't assume that everyone else knows what you know or is asking the questions you're asking. Wondering why something isn't being investigated? Bother your Congresscritter. Have a whistle to blow? Bother your Congresscritter. Better yet, let us know: a lot of the time, media attention can get the ball rolling when it wasn't before. Try scoop [at] motherjones [dot] com. We're listening.