Would anyone explain how rating is being changed at Bitcointalk? I've posted more than 14 posts in last 2 weeks, and the activity is 22. But I'm still newbie! How does it work?? 
You mean your ranks, how will you rank up. Here in this forum your rank depends on the number of your activities, and this activities are your post on this forum. 0 Posts: Brand New
1-29 Activity: Newbie
30-59 Activity: Jr. Member
60-119 Activity: Member
120-239 Activity: Full Member
240-479 Activity: Sr. Member
480-774 Activity: Hero Member
775-1030 Activity (random): Legendary
If your not that convinced just check the beginners help and guidlines at the Other section