As an aside to "holding wires, etc. in place", it's good to keep in mind that a good solder joint usually begins with a good mechanical joint. In other words, the solder isn't supposed to be a structural component of the joint. As much as possible, the wire/part should stay in place on its own before you try soldering it. Leads/wires should be wrapped or bent over their mating points where ever you can so there's already an electro-mechanical connection before you solder. Heat should be able to conduct between both items to be soldered so the solder can flow properly. If you get the sense that the solder is acting like a glue or caulk in/around the joint or the items are just laying against each other, then the only thing maintaining the joint will be the solder and it'll be weak. Solder is soft and somewhat friable, so it has very little structural integrity. That's the cause of many "cold" or failed joints.