Work-search log: how detailed does it need to be?

I have been applying to about 16 jobs a week as a store manager, but I am unsure what my state wants in the log. Some days I only network by email or attend a job fair. What do you record?

Keep everything in writing and save the confirmation numbers. It saved me later.

I was asked for my log once, after six months. Having it in a spreadsheet made it painless.