Admission to PA school is VERY competitive. Most applicants do not get in on their first shot. It all depends on your qualifications - i.e. health care experience, GPA, desire to be a PA, etc. The application process is similar to Med school. The essay is very important, and if you are fortunate enough to make it through the initial cut, the interview can usually make you or break you. This has been my experience. A good book to get is Rodican's "Getting into the PA school of your choice".
Best of Luck,
Mike