If you need advice on whether you need to open a partnership, proprietorship, or a limited company, here's an interesting article: [The Right Sort Of Company | Opinions - IN - Yahoo! News](http://in.news.yahoo.com/blogs/opinions/sort-company-065011573.html)
However, if you are asking the question on how to go about it, here are a few steps:
1. Get clients - To get clients, you need to show reasons why they need to entrust their search process to you rather than an established recruiting firm. To do that, you need to present a unique proposition that your competitors do not have.
2. Get candidates - Once you get clients, you need to focus on candidates that you need to present to the client. You can rely on job sites, but you have to realize that many other recruiters would also have access to them. Are there passive candidates that you have access to that others don't?
Hope that helps.