When you prepare for a college interview, it's important to do it early and be ready for anything that you might be asked. Of course, it's impossible to know each and every question that someone might ask you, but you should have a pretty good idea of the kinds of things that the interviewer will want to know.
You can have practice interviews with friends and family members, and you can also do some Internet research that will help you determine what kinds of questions will be asked of you. If you have a job you should have some idea of what the interview process is like, but that doesn't mean that you shouldn't practice anymore.
Interviews can be very nerve-wracking and you don't want to let a panic attack stop you from getting into the college that you dream about. You should practice enough to alleviate much of your nervousness, and you should know what to say to the kinds of questions that are usually asked, including what your strengths and weaknesses are. How you answer the questions is often as important as what you actually say.