BTW there is this great "reality" show on Spike called DEA. Follows DEA agents/undercovers busting drug dealers.
Always up the line, up the line. Undercover goes in, busts low guy, then up and up and up. I mean that's pretty obvious stuff but it explains how they get in and whatnot (seems so easy).
Good stuff right there. Actually if I was a criminal I would have learned a lot about their techniques by watching that show.