Thanks for the speedy responses. I think :) I'm making some progress here.
The wiring is in place for a three way switch. Only a single pole switch was installed however. I have 3 wires coming into the switch box. Each has a black and a white and a ground.
There are 2 lights (A) and (B) in the room. Only one switch currently operates light (A) and the other switch operates light (B). I want to keep it this way. One switch each.
Light (B) though has the wiring for a 3 way. But, only a single pole switch. This is where I want to put the dimmer. I tried just connecting the 2 leads (Both black) from the dimmer to the 2 blacks that operate the single pole switch. No good.
The single pole switch had a black wire connected to the sigle black and a black connected to the 2 joined black wires.
I'm thinking only one of the black wires is hot. Because when I uncouple the 2 that are together, light (A) goes off.
I really hope this isn't as confusing as I am confused.