When I first made my config, I just downloaded a bunch of pro player configs and took things from all of them.
If everyone used some setting I used it too.
If they used different values for some cvar, I got some information about that setting, and then I chose my values according to that.
(And I also tried to benchmark, and see if I got more or less fps)

Then I just kept improving my own config (and maybe, as I become more experienced, removing some non-existing cvars I had copied from other people's configs :p)