Since I just spent several hours trying to get my Dell 2405FPW monitor working with a Debian laptop Ill post the successful formula in the hopes of getting someone else through it faster.
Read it here
The key to all happiness: use the nvidia-settings utility. Really, the biggest problem with the advice you find on the net is that most posts are half-right. They get close to the variable names and values that you need in the conf file, but none of the posts I read were even close on the sections. In many cases Im sure this is because there are multiple ways to do it, and nVidia, whose drivers are proprietary binaries, knows how to make their own GPU work. Anyway, my advice is to use it. But first a few other things.