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.
Statistics even show that kids who participated in an extra curricular activity have less stress. The only thing is, is that they have less time for homework too. Homework takes away all of my free time to spend with friends and family; where I can just forget about all of my worries for an hour or two.