Make agreeable posts, get +1s(top right of a person's post), gain renown. It will come naturally, especially if you have strong/supported opinions.
Or if you are smart enough to know the whining of the community.
How to get fast renown :
-create a "NERF cav" thread. Try to explain a bit, but you can find the ideas in the other 10+ similar threads. Don't forget to add : "this is a serious suggestion". You'll get all the "+" of the whiners and cav haters.
-create a "NERF range" thread. You'll find archer's info on the 5+ similar threads, xbow's info on 2 or 3 threads. Don't forget to add : "But leave throwing , if anything else, it needs a buff." Will earn you some extra +. You'll get all the "+" of the whiners and range haters, and some "+" from throwers.
-create a "Change cav" thread. In there, you ask to "bring back old lance angle" and maybe lower a bit the hp of horses that cav don't use anyway (like the plated charger). You'll get "+" from the cav lovers.
-create a "Nerf Rusbow/Buff Longbow" thread. You'll earn the "+" of most 5 PD archers, who hate Rusbow, and the "+" of the MW Longbow user.
etc...
Important thing for renown is the "+", not the "-", so you can also do some stupid troll remarks, or post useless but funny gifs.
Renown is really not that much relevant of a person's usefulness or kindness on the forum.
Except for chadz. He's awesome, and it proves it.