Your vision regarding the size and nature of your business.
The level of control you wish to have.
The level of "structure" you are willing to deal with.
The business's vulnerability to lawsuits.
Tax implications of the different ownership structures.
Expected profit (or loss) of the business.
Whether or not you need to re-invest earnings into the business.
Your need for access to cash out of the business for yourself.

SOLE PROPRIETORSHIPS
The vast majority of small business start out as sole proprietorships. These firms are owned by one person, usually the individual who has day-to-day responsibility for running the business. Sole proprietors own all the assets of the business and the profits generated by it. They also assume complete responsibility for any of its liabilities or debts. In the eyes of the law and the public, you are one in the same with the business.

PARTNERSHIPS
In a Partnership, two or more people share ownership of a single business. Like proprietorships, the law does not distinguish between the business and its owners. The Partners should have a legal agreement that sets forth how decisions will be made, profits will be shared, disputes will be resolved, how future partners will be admitted to the partnership, how partners can be bought out, or what steps will be taken to dissolve the partnership when needed;. Yes, its hard to think about a "break-up" when the business is just getting started, but many partnerships split up at crisis times and unless there is a defined process, there will be even greater problems. They also must decide up front how much time and capital each will contribute, etc.

CORPORATIONS
A corporation, chartered by the state in which it is headquartered, is considered by law to be a unique entity, separate and apart from those who own it. A corporation can be taxed; it can be sued; it can enter into contractual agreements. The owners of a corporation are its shareholders. The shareholders elect a board of directors to oversee the major policies and decisions. The corporation has a life of its own and does not dissolve when ownership changes.

LIMITED LIABILITY COMPANY (LLC)
The LLC is a relatively new type of hybrid business structure that is now permissible in most states. It is designed to provide the limited liability features of a corporation and the tax efficiencies and operational flexibility of a partnership. Formation is more complex and formal than that of a general partnership.

The owners are members, and the duration of the LLC is usually determined when the organization papers are filed. The time limit can be continued if desired by a vote of the members at the time of expiration. LLC's must not have more than two of the four characteristics that define corporations: Limited liability to the extent of assets; continuity of life; centralization of management; and free transferability of ownership interests.