In the old days, it was usually best to pre-order a game as soon as possible. Now a days with Collector's Editions, and store exclusive content, it's best to wait until a week before hand and then pre-order it, just to assure that you will recieve your copy.
For example, I still have not reserved FF XIII since Best Buy and Gamestop are at war in trying to snag Exclusive content for all of the popular titles. In addition, FF XII's Collector's Edition was only available at Gamestop. Add the possibility of midnight releases, and you have to very carefully select where you purchase your game. I would highly suggest against pre-ordering for that reason.
For example, I still have not reserved FF XIII since Best Buy and Gamestop are at war in trying to snag Exclusive content for all of the popular titles. In addition, FF XII's Collector's Edition was only available at Gamestop. Add the possibility of midnight releases, and you have to very carefully select where you purchase your game. I would highly suggest against pre-ordering for that reason.