When should a numbered list be used?

Answer 1

A numbered list should be used where you have tasks or steps which should be completed in order e.g.:

1. pick up box
2. walk to living room with box
3. set down box

They should be used here because you cannot logically complete any steps before the previous, and the numbers indicate that an also so the reader doesn't do step 2 then realize they have to do step 1 first (not applicable to that example as you can't).

Other examples would be food preperation when you have to do things in order.

Also lists in which you would do any number of the things but are sorted for priority e.g.:
1. Eat and sleep
2. Play with son/daughter
3. Watch TV

You could do these out of order but hopefully you realize that Surviving is more important than entertaining your children, which is more important than sitting on your butt.