Know why you want to do what you want to do. I am pretty sure every school will ask you why you want to go into optometry. And be honest with yourself. Think about your future- where you see yourself in 5, 10, 20 years. Know why you applied to the specific schools- did a certain aspect of their program appeal to you? Do you have any anecdotes from shadowing experience? Be enthusiastic and show how excited you are for optometry!
Practice interviewing. If you are still in college, see what your pre-professional program can offer you. I know many schools will offer interview help. Optometry just isn't about the eye, it's also about how you can interact with others. These schools want to see if you can talk to people, so your interview skills can go a long way- if you are short, hesitant, etc., it might not help your chances (there was a thread a while back where a girl with good stats got rejected because she came off in the interview as very awkward). Basically practice, practice, practice for your interview- it will go a long way.