Most Helpful Girl
Well no one knows what the letters stands for exactly, but it's just a ranking system and the points can be used to redeem prizes like a GAG t-shirt, no ads, donations, TGIF gift cards, Amazon gift cards, etc.
The more you're on here/answer questions your xper points will go up, but there's also some other ways to earn points:
It can very if you login everday you can earn points. If you spend a lot of time on here asking and especially answering questions you can earn points. Getting most helpful earns you a lot of points also selecting most helpful to your question earns you points. Voting on a poll earns points. A good way to earn a lot of points is to follow gag on all of your social networks Facebook, Twitter, google+, etc. Another good way is to write a mytake submit it and get it posted on GAG. There's a lot of ways to earn points.
Just click this link it will tell you everything about XPER points and how to earn them. How many you can earn from what task you do, or how you can lose them, what how much does it take to get to the next level, etc.