Grom says we obey....Bow bitch bow!
He decides if you participate or rolle play, then hands out "x" points to each person at the end of each session. We gather the points and when enough is accumulated we get to spend it on our character.
How the points are used is the hard part. Each class has different uses for points, the level of each character has a lot to do with it as well. Remember class and level decides on how many points you need to progress.
I know this sounds very complex and mathematical, but its worth the brain power. If done right we can gain points very quick and progress in character development even quicker.
Jumping on the table and flailing around like a duck helps in gaining points. Sitting in the shadows projecting your thoughts the DM hoping he understands what you intend to do, but dont want him to truly understand will gain you MASSIVE POINTS.
Hope that helps