Getting a development job with any company as a graduate with little or no experience can be tough, and I doubt Apple is one of the easiest!
Being enthusiastic and confident (but not overbearing!) in your communications can help - if you submit a snail-mail CV/resume, a good cover letter can help make you stand out.
Showing any knowledge of the Mac will help greatly, but of course, there's no substitute for experience. If you had any Mac development experience, even if it's a very minor shareware utility or game, it might help. It'd show both technical proficiency and initiative.
I was very lucky, as Apple came to the college looking for students for work experience, and I was one of only a handful of Mac geeks in the class. Then when I graduated I had a job without even an interview.