We have a logbook, instructively labelled, "Logbook." Stowed in the rack on the starboard side of the companionway:
Inside are ruled pages with columns that have headings like "date", "time" "heading" "speed," "comments" etc... and during our first season we diligently attempted to keep a proper log. Hwever, while it was easy to log time of departure and note the sumlog reading and heading outbound, once off the dock record keeping deteriorated, and nobody ever remembered to log the return time or total mileage. By the end of the season entries looked like this, "Really big winds! Wheeeeeeeeeee!!!!!!!!" scrawled across the page, with no regard for the lines and columns.
That informal style has pretty much carried on, unless something really critical needs to be noted.