Realistically it seems unlikely you'll be able to make sufficiently huge an impression in the space of only a year, to outshine candidates who have been at the school throughout their secondary education. But be friendly to absolutely everyone, say hello, be the 'binder' who brings isolated people into discussions, show leadership skills, keep your grades high, get involved in a few extracurriculars. The most important of those is showing leadership skills (and that's rather a hard concept to describe).