To choose the optimal business structure, entrepreneurs should consider factors like legal liability, taxation, costs, flexibility, and future needs. The main types of business entities include sole proprietorships, partnerships, corporations, and non-profits. Sole proprietorships have unlimited liability but easy formation, while partnerships have two or more owners but all partners have unlimited liability. Corporations may have many shareholders but offer limited liability, though they have higher formation costs and ongoing regulatory requirements. Non-profits are formed to serve a social purpose rather than generate profit. The best structure depends on an entrepreneur's individual circumstances and goals for their business.