First, welcome to RIU. You basically build rank on here by posting advice in the forum threads. This is not to say that offering bad advice will build you rank. Also factored in is the number of +reps. I don't know excatly how everything is weighted.
Don't get too concerned with the titles listed under your name, it has more to do with offering good personal knowledge as well as book knowledge and building your reputation in this manner. There are many people with lots of rank I wouldn't trust to grow a radish. There are also many great and informed people which are newer to the site and not developed the ranking yet. If you are looking for advice and want to accept it, check out the person's other posts, he/she or it knowledgeable or just say anything to make a post.
Most serious growers here will check your grow journal and your post before they blindly accept advice soley based on ranking.
So share your knowledge and build your rank.
Again welcome and Merry Christmas