theres nothing i can tell you that isn't obvious... but i'll say some things anyways.
-make it heavier
-drive like 30kmph and make no sudden movements
-place some wood on each side of the sub so it has nowhere to move
-depending on what your driving you could bolt it down in like 2 minutes, but then you would have a hole in your trunk.
mine never moved, but the box probably weighed 50lbs, and it was big.
