You will need a business plan, a prototype of your service or product and a list of potential investors. The business plan should contain (1) description of the value your service or product will create; (2) assumptions about the perceived value (demand) (3) revenue model (how the value will be monetized) (4) projections about the needed investments; (5) projections about the income (6) projections about the ROI - return on investment (beware it does not appear with the minus sign in front! :)))) Once you make contact with the investors, you will show them the prototype and ask them to help you cover the expenses of a focus group survey. This survey will help you fine-tune the model of service and the business plan. Next you will make a marketing plan. Then sign a contract with the investor for some money to start. You might decide on bootstrapping here. You will gather a team, rent necessary equipment and/ or office space and so on. And that's it in brief.
The words in italics are specific terms. I would be glad to explain them in detail but I will leave this task to you for three reasons:
You can learn about them by simply performing a google search. There is tons of information on each of them. Wikipedia is a good starting point. Or these two: http://www.businessplans.org/businessplans.html and http://eu.knowsleycollege.ac.uk/EVEC/index2.php
It is a daunting task for one person to explain them all;
I am just a novice in the entrepreneurship field and I might not be understanding them the right way.
Here is my disclaimer: the scheme described above is just a suggestion I find useful for me. There could be mistakes in it and there could be much better ways to make the first steps.