At the very least you use a dab of sealant at the four corners where the heads meet the block at the intake area. I also use sealant at both ends, but NOT on the intake surface itself (around the ports).

As far as adding extra gaskets, I add them as space allows (often there is no room for them and still be able to start the intake bolts). If there IS room, I like to super glue the gaskets to the valley pan to ensure they don't walk.