Being US-based helps. Also, I would reply to postings asking for more clarification on an item. This does two things. First, it shows that you understand the work better than the client. Second, it gets the client comfortable talking to you.
I recently joined Toptal and was shocked to have my rate set at $30/hour. I got them to raise it to $40/hour, but that's still nowhere near what I was earning working as an independent contractor or even what I can get on Elance.