Building a shot list is more than making a list of products. It should also take into consideration time of day, time per shot, location and number of views/scenarios needed and talent. An experienced art director can help develop a focused shot list that takes these things into account. It seldom all goes exactly according to plan and you have to be adaptable. A shot list is a goal and it's good to try and leave a little breathing room in it because you'll probably need it.