All the reading I have done in the forums suggest that moving up tiers is based on a couple factors. I think, and the key word here is think, that you have to carry a certain average with a combination of a certain number or ranked rounds, or tournies. For example: From hack to amateur you would have to have 5 rounds with a minimum of 70 average. That number is totally made up but I think that is how it works. Amateur to the next tier would be like 20 rounds with a minimum average of 65. Again, totally fiction number. I just wanted to demonstrate how it increases with each tier.
I am not sure but I do not believe that WGT has ever officially released the exact formula although there are many members that are real close with their estimates. Do a search for something like "tiers" or moving up "tiers" and you will find a bunch of information.
Also, practice rounds I believe do not count as they also do not count toward your average. I am new as well so this is all I can offer for help right now. Good luck my friend.
-Nuke