There are several different methods that silversmiths use to create their pieces. Every silversmith has their own methods and trade secrets. In fact, methods can greatly differ from smith to smith, and I am going to describe the two ways that I have been showed.
According to the person who first introduced me to silversmithing (pictures here of that lesson), three different solder types are used: Hard, Medium, and Soft. These are so called according to their melting temps. These are used so that when the torch is being used to melt one piece of solder, it will not melt a different piece that has already been used. For example, to solder the bezel, (the strip of silver that holds in the stone) hard solder is used because it melts at a relatively high temperature, and when soldering the bezel to the plate, medium solder is used. This makes it so the medium solder melts and runs before the hard solder: if they both melted at the same time, the solder at the seam of the bezel would run off, and it would look like a crack in the bezel.
The style that my current teacher uses is different. He only uses one type of solder, but, to make up for that, he uses something called flux. Flux is a type of paste that sort of attracts the molten solder, so before soldering a joint, he first spreads a little flux on top, then gently holds the torch over that spot. The flux begins to sizzle, then starts to get hard. Right at that moment is when he applies the solder. For a second he moves away the torch, puts a bit of the solder in place, and then re-applies the torch, melting the solder where it flows immediately the joint.
There are different methods, one is not essentially better than another, but I am discovering that every silversmith has their own little style.