In these of unleaded fuel, you may use spark plugs until the electrode erodes away. Every-so-often, check the center electrode for a sharp edge. As slowly rounds off, file it sharp.
Admissions officers look first at test scores, the rigor of the courses you take, and your grades in those courses. After that, they are interested in a student's extracurricular activities -- in other words, how you spend your time outside of classes.
Also notice that the admissions offices do keep track of your contact with them, including whether you visited, attended a college fair, or spent the night. As you can see, your curriculum, your GPA, and your class rank are all very important.