Unless you're working professionally or in a sailing class, there are no strict requirements for keeping a sailing logbook. It's still a great idea to keep one, however. You can make it any way you like. There are dozens of options available online to start with as a template, or you can make your own with a generic notebook. You can record any details you like. At a minimum, make a new line for every trip. Usually, people record the date and time, departure and destination, engine hours ran, fuel used, weather and sea conditions, and any passengers or notes.