Qualifications
You might expect this section to include the phrase "smash rocks good" and that's it. Well, that's part of it, but there's a whole lot more to it than that.
First off, yes, generally you do need to smash rocks good. This means you're going to have to be physically capable of working with stone. Lifting it, moving it, shaping it, changing it―this is manual labor at its finest. Hand-eye coordination and above-average vision are also important, because you're going to be using dozens of tools to shape, craft, and build with stone. Precision is key in this field.
You're also going to need things that only come from the power of humanity's greatest muscle: the brain. (Yes, we know that technically the brain isn't a muscle, but just humor us.) If you don't have a high school diploma or equivalency, good luck finding a mason willing to apprentice you.
Attending a vocational school will definitely help, if you're young and already determined to be Stonemason-4-Lyfe. Either way, you should really pay attention in math, English, and shop―the skills you learn in these classes will be put to use every day.
Finally, there's that little emotion known as fear: This job will likely involve heights, blades, machinery, and electrical generators. If you go to work every day terrified you might lose a finger, put the hammer down and check out some of our other fabulous career guides.