The most important choice, maybe after picking a global topic for your wiki, is the choice of the tool you'll use as a fondation for your knowledge base, and this one may lay on personnal taste to be honnest, and it will depend on the technologies you have installed on your host server, also on the functionnalities you want your wiki to have, the personnalization, plugins, security, login method…

While this may seem overwhelming, you could also be in our case and just want it for personnal use, so you could choose almost any wiki service.
Here, Dokuwiki seemed like a good choice because it's pretty common and we worked with it as users before. Also, the installation process is, as we'll see later, pretty easy and quick (and well documented on Dokuwiki's wiki).