Game play question.

[zap]

When using smoke in an advance. where the enemy is in the hex adjacent to the hex you will be entering. Should you drop the smoke in the hex your advancing to or the hex where the enemy is. I'm looking for the best protection against op fire while advancing. Or is there no difference in the cover it gives. I've used smoke in both hexes before so i know that is the best. However, when the number of smoke you have available is limited you want to be frugal. So which is best when you can only use 1 smoke round so its most effective