Remember, it is all very well to tell an eight year old girl that you have chosen her flower girl dress (and often this is not easy!), but try informing twenty or thirty something adult bridesmaids what you would like them to wear for your wedding without consulting them! Believe me, they will not be happy!
I hate phrases like wedding diet and bikini fit, because they imply a burst of discipline and stricture that just isn't sustainable after the event takes place. Worse, you may find that it doesn't give you the results you wanted. So this is a short guide to what worked for me, and what has sustained.