STEM is very broad coterie of majors, in particular, what qualities pertain to a person interested in STEM?

First, I'd like to commend you on your interest in STEM, followed up with career exploration. Let's begin by looking at the platform of disciplines: Science, Technology, Engineering, and Math. You mentioned your interest in science and math. All of the disciplines in STEM have a common course denominator, do you know what it is?? Yes, math, one of your strengths. You will need a solid math background for the many of your science classes; such as, chemistry, physics, and any others with a math connection. The life sciences; such as, biology, anatomy, physiology, and related ones, not so much. Technology, whether computers or related, will require analytical and problem solving skills...math. And lastly, engineering, will most definitely require math proficiency in the higher level classes. Sometimes students fail to do their "career homework" and are thus unprepared for the expected math proficiency in computer and engineering college courses. What usually follows is a change in their undergraduate major. The same can happen with an architect student who assumes it's all about designing drafts for houses and buildings, not realizing there's an element of math in the process.

If you're still in high school, plan on taking as many rigorous math and science classes that can reasonably fit in your four-year plan. Be sure to take the ones required for graduation. If you're in college, the recommendation is the same. If you haven't started STEM career exploration, that's your next step. Information is easily available through College Board's Big Future, Naviance's Family Connection, Choices, and just Googling STEM careers. Consider the possibility of a STEM summer enrichment program, if you're in high school; if in college, check your student services office for an internship. My oldest son (43) is a civil engineer and his interest started from a summer enrichment program he attended after 10th grade. The next summer he participated in the SEAP engineering apprenticeship and earned a generous eight-week salary for a 16-year-old.

Hope this helps!