Lets say I want to install JUST one app (PrP or Prelude in this case) from my CS6 DVD. I only installed stuff I needed at the time. How do I do this?
Choose the custom install option on the DVD startup screen and uncheck everything you don't want.
Remember that the products within a CS6 collection cannot be installed as point products scattered on different machines - even if you only use part of the collection it still consumes one of your collection license seats.