When would you "slot" points in backgammon?
This depends heavily on what the opponent has done so far with his runners. If both runners are still on your 1 point, or if only one runner remains in your home board, slotting forward from your 6 point often has a good risk reward. If two split runners exist in your home board (or one runner and one or more opposing men on the bar), you must be much more cautious slotting in your home board.

Additionally, the thickness of your wall to date allows more aggressive play moving it forward. If you have pointed on 5-6-7-8 already, slotting on 4 might be considered even against split runners, but the shape of your opponents home board is important also. 

Weighing all these factors is good judgement, which comes only form the experience of having made decisions with bad judgement and learning form it.