It's a great question, for sure. (My background: was a software consultant then a marketing consultant, total of 5 years of consulting. Now inhouse, never was a fulltime freelance consultant).

If you're not sure what your expertise is, I'd say FT freelance consulting might not be the right gig for you right now. Instead, maybe try working for an agency for a bit to find what you are really good at. Then start putting yourself out there on the Internet to start attracting those clients (through blogging, relevant online forums, etc). I've never been fulltime freelance as I said, but I still get multiple freelance inquiries a week even though I've not done freelance work in over a year.

The business stuff - ie how much to charge, how to structure projects, etc - can be learned. But you need to learn how to drive demand and show your expertise first. Honestly I'd recommend doing a lot of reading on inbound marketing, conversion rate optimization (which gets into psychology), and how to generate traffic online.

Hope all this helps. Happy to hop on a quick call to hash through ideas if you'd like!