... I would also add to Kara's comment one important note - avoid loans. Figure out how you will get money for the study. As far as I know it is quite expensive to study at UCLA or at any other university in the US. 

Depends on what you plan to major in, but typically: get good grades, participate in extracurriculars (performing arts, sports, especially volunteering), high SAT (or equivalent test) scores, pass advance placement (AP/college level) tests, and individualism (be yourself!).

I did not go to UCLA, but rather its Texas equivalent, UT.  I would think the same would apply for UCLA.  I hope this help!