How does a case get to the US Supreme Court?

Typically, a case will reach the Supreme Court through an appeal by a circuit court. This normally happens after a smaller court reaches a decision where a party is dissatisfied, and it decides to appeal to the Supreme Court. From there, the Supreme Court can choose whether or not to take on the case. Four of the Nine Justices need to agree in order for the Supreme Court to accept a petition and reply in the form of a what is called a Writ of Certiorari, which basically is a Writ that informs the smaller court of a request for review. Thousands of cases are appealed to the Supreme Court yearly of which only a few are accepted. Those not accepted can still be appealed at the lower level.

Less often, a case will reach the Supreme Court through an appeal from a State Court. Cases tend to be accepted mainly when dealing with constitutional law, but in general, States try to keep the Courts separate to preserve State power. The way the case makes it up to the SC is similar to that of the circuit court, but the appeal comes from the State Court.

The final, and least common, way the Supreme Court will hear a case is through "Original Jurisdiction", which is when the Supreme Court hears a case directly, skipping any lower court. This tends to occur in cases where a federal political figure is involved, such as United States v. Nixon. Other times this occurs is conflict between states such as State of New Jersey v. State of New York.