What to record each day
Who was on site, what was done, deliveries in or out, delays and their causes, weather that affected work, and anything unexpected.
Why digital is easier
Dates are added automatically, photos sit alongside the entry, and nothing gets soaked or left behind. Searching for what happened on a given day takes seconds.
Keeping it honest
Fill it in on the day. A diary written from memory at the end of the month is much less useful to everyone, including you.