Most heroes enter in their own diary entries by deciding what they feel is relevant to include (and what to exclude). However; any heroes that manage to collect a Diary-entry generator often slack off while it generates entries. The programmers of this generator do have a sense of humor - rumors are that it claims item sales that a hero never made, purchases of items heroes wish they had, and includes embarrassing entries such as having the hero run from monsters they never actually encountered.
Some heroes upon discovering this misinformation will decide to sell the item while others will keep it for their amusement so they can spend their time doing other things like drinking beer in the tavern or playing games. Heroes who use it too often or too long will have a hard time actually entering things into their diary for awhile.
There is a non-magical, identical item in every hero's inventory, but this is usually called a pen. It is important to note that your hero must actually have the ambition to use this as no voice commands sent related to entering something into the diary will be heard.
The only requirement of using this item is finding one in the first place and managing to have your hero like it enough to keep it. This artifact is large, heavy, and cumbersome and can also be sold for a decent number of coins in the shop. Heroes too lazy to tote it around may ignore the fact that it allows them to be too lazy to enter things in their diary.