Best Practice For Documenting a Server

You guys are so great with helping me out along my way to becoming a great Admin. I have another question tat might seem dumb, but I want to know the right way.

I am in the process of documenting different things on my network and I have came down to the Servers.

What are some key things I should document about these servers. SO far I am thinking the obvious: ipconfig settings, which are domain controllers, what applications are on each….

What else should I look for and/or pay close attention to.

Any and all of your opinions are greatly appreciated.