It is worth rethinking how detailed documentation is needed. If you work in a very small team and have the possibility of continuous communication while working on the game, it is actually enough only to describe the individual elements of the game, because most and so you will still agree with each other. In such a document should mainly find the most important features of the game, their action, the outline of history.
In the case of larger teams and projects, you need to approach the subject documents slightly differently. Use your game designer skills to create a document that will not discourage the reader. A wall of text that attacks its monotony is probably the worst you can create. Do not be surprised that the benefit of such a document can be quite sleazy, because not everyone (although it should) will read it carefully.
I am a fan of breaking things up on individual elements, which perfectly interacts with the Wiki in which you can create descriptions of specific mechanics, characters, parts of games and put in the text links leading to other things that are related to them. Digital documentation has one big advantage over paper: You can place animations on them. This can be very helpful if you already have some parts of the game, but want to change their performance.
Note that the image conveys more than a thousand words. Instead of describing something through a few pages, you can draw this by placing the appropriate brief descriptions. Diagrams are also a great useful tool to help you understand the relationship between different game elements. For example, in a certain game, we describe who he loves.
Quiet lover loves Luz has Ryję dollars, but she does not love him. Dollars loves Alphonsus without reciprocity and Edmund, who also loves her. Edmund, by the way, is also in love with Alphonsus.
Design changes are inevitable, for this you need to make corrections in the documentation. The Wiki has the ability to check previous versions of the document, but it is not too convenient. I propose to change the text along with the appropriate highlighting and describing what has been changed. Super in the Wiki is also that everyone can instantly add their comments!
A nice thing about creating a dossier is to specify things (sounds, code, graphics, levels, etc.) that need to be done by specific people, so that the level designer knows which graphics to report, for example, if an element environment requires changing… Well, because something.
It's a nice thing to use the production milestones. I don't mean milestones, or rather small achievements, that are quite close. This allows people to feel close to their goal, which is to finish creating the game. Let it be, for example, to complete the creation of a weapon timesheet or to finish programming the character movement model.
Also, remember that the document will not replace your meeting with other people in four eyes and convey them to the heart of your project. Talking to people will be more inclined to talk about the feelings that the game has to evoke, which will allow others to better understand the whole concept.