How do you solder copper pipe fitting and valves?

I've done a lot of electrical work around my house, but I've never done any plumbing before. The guy at Home Depot told me that I need to heat the fitting, but not the pipe itself. He also said that valves (the new ball type) are easily destroyed by overheating. How do I know when the pipe and fitting is ready to accept the solder? How do I avoid damaging the valve? How do I know how strong to turn up the flame on the propane torch?