Well Cameron,
We all wish that we could tell if and when we are going to have luck with breeding newts/salamanders. The truth is, there is no way to tell if your slimy salamander is going to be a mother. A good friend of mine knows a guy who breeds P. glutinosus (slimeys) outdoors, but I have never heard of it being accomplished in an indoor set-up. I suppose if you really wanted to, you would separate the sexes in different containers, and keep them cool (38-45 degrees F) for several months. When you take them out, they might produce eggs, but with that species it may be very difficult.