Freshman student, just moved in. An inquiry about textbooks.

So, I just moved in today. So far, things have gone well. However, as the start of classes near, I'm starting to worry about getting textbooks. Most people I've talked to suggest using the IBX, but people have also told me that I should wait until I have my syllabus before I buy books. Any suggestions from returning students on how I should handle purchase of my books?