If I were to start a business from scratch today, the first place I would start is not with what form my business should take. Everything in business should flow from one place: the customer. What the customer wants, how much he or she is willing to pay, how we will solve the customer's problem, and so forth. If we start an S corporation or an LLC can be thought about and done later on.
The main reason we start at the customer and solve his or her problem is because we need the foundation of a product that will sell for a profit. One that will continue on for years to come. Without that, there is no business. If you go all out and start a business without this kind of product, the business is likely to fail. In fact, even if you come up with a great product, you still have a high risk of business failure. But without a great product, it is almost a certainty.
The Customer's Problem
Finding a problem to solve is finding an opportunity. You add value when you uniquely solve a customer's problem with a product they can buy.
What is a product?
A product can be a physical product such as a shovel, a digital product such as an eBook, or a service such as business consulting. It could also be a method of distributing that adds value, or a way of organizing or combining existing product lines. Really the product is up to whatever you can imagine.
Initially you can sell under your own name, which is the same as a sole proprietorship. If you find that your product sells, you can always sell your sole proprietorship to your corporation or LLC. But until you find a product that really sells for a profit, you should continue using trial sales.
What problem do you have?
After finding a product that sells for a good profit, evaluate your own business problems. Evaluate how you can serve the customer better, your concern for liability from damages or injuries, potential cash flow pitfalls, and so forth. Incrementally improve your business as you discover your own problems, especially focusing your attention on the customer. At this point you will probably want to consider business structure.
Have you run across a customer problem to solve? Can you create a product that will solve it?