... what's the criteria for one of these? Thanks in advance.
Because of the massive amount of spam that we get, we restrict access to user profiles for new users. That means that when you join, you won't have access to a profile picture, profile editing, signatures, etc.
You've already hit the first milestone - I believe 10 good posts is the requirement to upgrade from "Newbie" to "Registered User," which is a title you can see underneath your username. The next milestone comes at 30 posts, I think. You'll also need some reputation points - these are points given by members to members for making great posts and threads. Why they're given varies from member to member - maybe it's for being friendly, maybe for being helpful, maybe just for posting something cool or getting a great discussion going.
As you get reputation points, the green bar below your username will grow larger and your "Rep Power" will increase. I believe you get 1 rep power for every 100 reputation points you gain - something like that. You can only give as many reputation points away as you have rep power. You can also only give reputation points to a user once in a row - you need to spread out who you give points to, in other words. I think after you give rep to a user, you'll need to give it to three other (different) users before you can give it to the first again. Even if you can't give someone rep points though, you should be able to leave a 0 point "agree" or "disagree" message by clicking on "Give Rep," a button with a little star next to it located below other members' posts.
Reputation points can also be taken away, which will change your green bar to red. Points are taken away for as many different reasons as they're given - being a jerk, making unsubstantiated claims, spreading SEO myths or incorrect information, etc etc.
Anyway! To prevent spam from getting out of control we don't reveal the whole secret sauce (as far as I know). But basically, keep interacting and eventually you'll get enough rep points and stuff that the ability will unlock naturally.
Hope that helps!