The first thing you have to do is come up with a product/service. The most efficient way to do this is by thinking of an idea that is needed in the world. What seems to you to be missing? One of the reasons Uber was so successful was because there was a real lack in the world for this service. It really is that simple.
Second, create a prototype that you’ll then show to a large group of people and get their honest reaction. If this is positive, move forward. Find someone to work with. Even better, find a sound investor.
Third, register the business and make a meeting with an accountant and lawyer. Do all the official stuff and make sure your company is legitimate. Always be aware of the importance of fundraising and attend lectures or go online to learn about the startup culture. These skills will put you in good stead for moving ahead with your startup.