The “exact steps” may be hard to define, but here are a few general things that need to be taken care of.
Business plan -- This is probably where you will start and a lot of this is based on your idea. Still, though, the business plan needs to be comprehensive and thorough. It will basically be a collection of a bunch of documents. Think about it as your whole business on paper. It needs to describe your business, set out financial and growth projections, have some form of market analysis, funding requests and other things of that nature. You want to make sure your whole business and anything related to it is on paper.
Filing -- Once you are ready to start, you will need to have your business incorporated / formed. First, you need to decide what form you want your business to take on (non-profit, partnership, LLC, etc.). Then you need to decide in which state you want to file. It may be your home state, or it may be another state. You need to make sure all appropriate and applicable forms are filed.
Tangible Tasks -- Finally, these are things like selecting a location, acquiring a building or securing suppliers. Any type of non-paperwork that physically has to be done before you can start running your business is what I mean here. But, keep in mind that paperwork may also come along with such tangible tasks (contracts with suppliers for example).
You can attempt to do these things on your own. But, this is very basic list and it is very important that these things are done right the first time. For that reason, it is better to seek an attorney to help you with the process. An attorney that has experience in this area gives a huge advantage to an entrepreneur.