Here is a picture of the inside of my kiln. You can see the glaze drips in it! I have a couple of glazes that run a lot. Learning the characteristics of the individual glazes takes trial and error. Once I understand what a certain glaze will do, I can use it more creatively. For instance, if I want a lot of blending of the colors, I will use a glaze that drips and moves a lot. If I want sharp detail, I use underglazes, which don't move at all.
Inside the kiln you see my bead trees. Once pieces have been glazed, they have to be kept separated. If they touch during firing, they will fuse together and be ruined.