It's a nice job if you can get it. The United States Supreme Court gets to pick and choose the cases it takes every year. On average, some 8,000 new cases are filed with the U.S. Supreme Court every year, of which they pick some 80 to hear and decide. So where do these 80 cases come from, and how do they end up before the highest court in the land?
TL;DR (Too Long; Didn't Read)
Most cases heard by the U.S. Supreme Court come to it as appeals from decisions issued by of one of the 12 federal Circuit Courts of Appeal.
Picking and Choosing
No case is so important that it is guaranteed a place on the U.S. Supreme Court's docket. There is no such thing as an appeal of right to the highest court. Instead, a party who wishes to appeal the ruling of a Circuit Court or state court files a document called a "petition for writ of certiorari" with the Court. This is basically a request for an appeal to be heard.
The Supreme Court votes on whether to hear the writ, and it only hears cases when at least four of the nine justices vote to grant a writ of certiorari. Usually the Court decides to hear cases only about issues it considers important, and many times it takes cases to resolve conflicting opinions by Circuit Courts.
There are only three pathways a case can take to get to the Supreme Court. It can reach the Court as an appeal from a Circuit Court decision, as an appeal from a state supreme court decision or as a matter of original jurisdiction.
Circuit Court Appeals
Without question, most cases reach the Supreme Court as appeals from decisions of one of the U.S. Circuit Courts of Appeal. Other than the Supreme Court, the Circuit Courts are the highest level of federal court.
The federal court system divides the country into 94 federal judicial districts, each with its own district court system. The 94 districts are grouped into 12 regional circuits, and each circuit (one through 12) has a circuit court of appeals. The appeals courts sit in panels and review district court decisions, determining whether the law was correctly applied. A losing party can file a petition for writ of certiorari with the Supreme Court if he wants one more bite of the apple.
State Court Appeals
The second most common way a case can reach the Supreme Court is as an appeal from a state supreme court decision. Every state has its own highest court that is the final authority on interpreting state laws. However, the U.S. Supreme Court might hear appeals from state supreme court rulings that involve the U.S. Constitution.
Under the Constitution, the Supreme Court has original jurisdiction for a narrow range of cases including states suing other states, the federal government suing a state, and cases that involve an ambassador from another country. This means that the Supreme Court can be the first court to consider the case rather than waiting to hear an appeal. The Court still gets to decide whether it will take these cases. Very few cases are heard under its original jurisdiction authority each year.