Area51 frequently refers to your commitment, and how many people fulfilled it, and that you haven't yet but if you will, you will be able to commit again... However, I found only one way to re-read what it means to fulfill your commitment: by going to another proposal in the commitment stage, clicking on the Commit button, reading what it says, and clicking cancel. Not very intuitive, if you ask me. The faq is also vague: "Once you've fulfilled your commitment on a new site by asking and answering a few questions, you'll be able to commit to another site."
Would it be possible to repeat this on your user page, maybe even with a progress bar for your own commitment, and certainly in the mails that are sent to users at the start of the private beta and after a few weeks? Currently users only get information that they should do something, but not what this something is.