Unlike a comprehensive shot list, a must have list allows me to pay attention to those extra special details that you would love photographed.
Write down any family formal groupings you'd like to get, separating each person within a group with a comma. Then separate each "group" by placing them on their own line. Here's an example...
Bride, Groom, MOB
Bride, Groom, MOB, FOB
Bride, Groom, MOB, FOB, Siblings
Bride, Groom, MOB, FOB, Siblings, Etc..
Each line item becomes a "group" or photograph.