SCOTUSBLOG on getting cert.
Scotusblog has a podcast on what type of cases the Supreme Court accepts. Gist of it:
A typical Term will have about 7,500 petitions for cert., but most of these a prisoner petitions, of which only a few will have any interest. It really boils down to about 500 serious petitions, of which the Court will take about 75-80. The keys to what it takes to go from one of the 500 to one of the 80 appear to be:
1. It must involve as near as possible a pure question of Federal law. The more heavily the case is dependent upon facts, the worse its odds are.
2. It usually will involve a split between Circuits, or State supreme courts, on that issue. The Court values its function of making federal law uniform.
3. The issue must be ready for the Court. No reason to leave it "percolate" in the lower courts any more, in hopes that they'll discover new angles or approaches.
4. The issue was clearly presented in this case -- it wasn't just a side issue, on which the parties and lower courts might have spent relatively little time and thought.
5. The lower court got it wrong. In theory, this wouldn't be a factor, but since about 75% of Supreme's rulings end in reversal, it obviously is. Note that this is the last criteria. Supremes rarely take a case just because they figured the Court of Appeals ruled incorrectly. But if you meet all of the first four criteria, the Court of Appeals erring helps to make the cut.
As the comments note, there are certain narrow exceptions. When a case can ONLY be brought in the Federal Circuit, there will never be a circuit split. I've also noticed a tendency to take a lot of cases relating to a new Federal statute with lots of regulatory twists. When the Congress wrote or re-wrote the pension laws a few years ago, the Supremes took quite a few cases on them. I'd assume they were figuring to lay out the standards early in the game.
It's noticeable that a Second Amendment case could easily meet all five criteria. It's usually a question of law (tho it would help to focus upon one or a few statutory provisions, not all the provisions of an elaborate gun statute), there's a big circuit split after Emerson, the issue has been percolating in scholarship (and with Emerson and Silveria, in the circuits at great length) for decades, and it's usually presented as the main issue of a case.