I agree with STL, especially with "don't be obnoxious." Someone once asked me (when I was a tour guide) "why should I pick your school over X, Y, or Z?"
Personally, I found that off-putting. Kinda a snobby "I'm not sure your school is good enough for me." I kinda wanted to say "pick us over them? you'd be LUCKY to get accepted here." Remember that the people working and attending wherever you are interviewing probably love their school. Even though on the surface the question seems really fair - a way of saying "hey, what are your school's strengths" - it could come off wrong and make you sound pretty arrogant. Not that you shouldn't ask about a school's strengths - but be smart how you ask. And act confident, but don't ever go over the line and give someone the impression you think you automatically deserve an offer. You don't.
Don't be afraid to say "I don't know" if somehow you get asked some 'fact' kind of question.
For behavior questions - find an answer that <actually> fits the question, because their whole goal is to evaluate you for certain behavioral characteristics and each question has a specific characteristic in mind. Giving them some super impressive story in your background that doesn't actually address the question .... doesn't help you. Don't hesitate to use non-veterinary answers for behavioral questions. 90% of my answers were drawn from my family or (non-veterinary) work background. If they ask you a question about conflict resolution and you say "I can't think of a good example, but look - I built the Taj Mahal and it's pretty cool!" ... well, great, but you just blew that question.
Be genuine. Be open. Smile. Ask (legitimate) questions. It's good to be excited, just keep yourself controlled.
Same advice I've given for years now: To prepare for a behavior-type interview, two good things to do: 1) Go to wherever you relax best. Get in a nice, relaxed, contemplative, meditative state of mind - think back on your life chronologically. Things you've done. Relationships you've had. Conflict you've been in. Accomplishments. Just ... fire the neurons to bring them to mind. 2) Google 'behavioral interview questions' and find lists that include things like "Tell me about a time you were in conflict with a co-worker, and how you managed it," print out the list, and take a friend out to coffee and have them fire 10-15 of those questions at you. Answer them just like you're in an interview.