If you are working by yourself, you may wish to have a business lawyer to create an limited liability company (LLC) or corporation for you. If you have any partners in the business you will want a formal agreement among you--the kind of agreement depends on what kind of entity you create. An accountant can probably advise you well about the best form from a tax perspective.
If you lease space for your business, you should have a business lawyer review and/or negotiate the lease.
I would suggest someone who routinely helps small businesses get started.
