OK, so what happens if I don't tie pin 12 to pin 9 or Vcc (is the latter a power supply point?). I don't usually mess with soldering but if I have to tie pin 12, how do I do that - use a soldering iron and solder a wire on the back of the board from the base of pin 12 to the base of pin 9?[/QUOTE]

Well, letting the pin "float" is lousy engineering practice and it might be susceptible to stray noise. But nothing really awful will happen under normal circumstances.

You needn't solder the stuff. For example, I will sometimes use wire wrap (AWG 30) wire wrapped around a a couple of pins.