First, Aeria has to open applications for the GS position. Watch the Wolfteam Forum
section (usually general discussion) and Aeria's General Announcements.
You don't really need a tutorial to be a GS. In depth knowledge of the game and the ability to handle yourself in a very public position are important. It's helpful if you're the kind of person that is easily available - you should be in-game and/or in the forums as much as you can. Maturity level and being nice in general can play a factor too.
You should also know how to handle player problems and complaints. Be able to help others do things like send in tickets (about anything - glitchers, hackers, missed promo items, whatever you can think of), and be familiar with Aeria/WT rules and the ToS.
No one can 'vote' for GSes. Who is and who is not a gamesage remains entirely up to Aeria staff.
...and I believe there is also a minimum age to be a GS - 16 I think, but I'm too lazy to look it up and see for sure. x_x