In general, I try to approach all new experiences in my life as learning experiences, and on-site interviews are no exception.
Whether you're a Comm student who's been prepping for investment banking interviews since you started middle school, or a liberal arts major just hoping to have a job before you graduate, everyone has to travel to a company's office for an interview at some point. This can certainly be an intimidating task, especially if it's your first time doing an on-site interview, but even after doing only one I feel I've gained a lot of valuable knowledge that I can take with me into future interviews.
1. Once you hear about the interview, get your travel plans confirmed ASAP
In my opinion, there's almost nothing more stressful than frantically trying to book a flight, train, or even an Uber at the last minute. Depending on how much time you have before the on-site interview, don't be afraid to ask the company about your travel reservations as early as you can. That way, if something goes wrong and you have to take matters into your own hands, you can still get some sleep the night before your interview.
2. Study up on the company and prepare thoroughly, but be sure to relax the night before the interview
It's definitely to your advantage to have done an in-depth scan of the company website and learned about their history, current projects/clients, motto, and generally what they do. Still, if it's not going to be an overly technical interview with lots of very specific questions, there's no sense driving yourself crazy with preparation and staying up super late the night before the interview trying to memorize every single client they've ever worked with. It's more helpful for your overall disposition to relax a little with some funny YouTube videos, your favorite album, or a few hilarious episodes of The Office.
3. Be prepared to talk about each part of your resume in GREAT depth
If you're interviewing with multiple people throughout the day, it's likely that they'll each ask you about a different part of your resume, so they can piece together a full picture of your experiences at the end of the day with the other interviewers. It's great to know everything you want to say about your most recent job or internship, but don't discount whatever job or two came before that, as those might be all your interviewer wants to talk about. Your interviewer might also be intrigued by something on your resume that you considered a total afterthought, but if they ask you about it, make sure you're ready to explain why it's relevant to this job.
4. Email your professors in advance and explain that you have a good reason for missing class
Some professors will be more understanding about missing class for interviews than others, but in general it's always best to tell your prof ahead of time, especially in smaller, discussion-based classes. They may still dock you a participation grade for the day, but at least you're moving one step closer to participation in post-grad employment.
5. Wear clothes that are professional, comfortable, and make you feel confident
With an on-site interview in your near future, you'll likely be turning to the stiffest, least comfortable, plainest outfit in your closet because it "looks professional." That may be the case, but if you truly hate wearing heels or have a blouse with a super fun print that you love wearing, follow your heart and wear the outfit that feels more like you. This may not be the time to break out the ugly Christmas sweater, but a fun tie or a brightly colored shirt and cute earrings could help make your first impression as likable as possible to everyone you encounter.
6. Don't be afraid to let your genuine personality shine through in your answers
Of course, in an interview setting you definitely want to be professional and not joke around TOO much with your interviewers. But when you're on-site and interviewing along with 20 other candidates, it's a long day for the interviewees and the interviewers. Everyone appreciates when people act like people, not like robots, so feel free to crack a joke or two or get excited when they ask you what you're most passionate about.
7. If you're offered bathroom or water breaks throughout the day, DEFINITELY take them
After talking emphatically for 2.5 hours straight (or more), your mouth might feel as dry as sandpaper, so hydrate as soon as you can. And if you feel like your bladder might burst after that Aquafina water bottle you just downed, feel free to take advantage of any chances for bathroom breaks that come your way. Taking a quick bathroom break can also help you take a quiet moment to be with yourself and collect your thoughts before you proceed with the day.
8. Prepare yourself for some off-the-wall questions, just in case, so you're not caught off guard
I'm not saying that you should have a concrete explanation for why a seal is your spirit animal when you prepare for a consulting interview. But be ready to talk about things not on your resume, like books you enjoy, other hobbies you have, or what your friends think of you. The company is likely trying to get a sense of your overall personality and whether you'd fit in in social situations, not just everyday professional ones, so don't be afraid to share interesting tidbits about yourself.
9. Smile and be friendly to everyone you meet, especially the receptionist
I once read online that some companies specifically ask their receptionist about the candidates that come in for on-site interviews, even though they weren't officially the ones conducting those interviews. This is just part of common courtesy, I think, but in the midst of a tight travel schedule make sure you try to be as polite as possible with any questions you ask or instructions you receive.
10. Use the whole day as a valuable learning experience, regardless of the outcome
In general, I try to approach all new experiences in my life as learning experiences, and on-site interviews are no exception. They'll help build up your stamina for future interviews and long-form professional experiences, and they'll also expose you to more detailed insight into how companies operate and structure their various departments. It's hard not to beat yourself up over minute details on the car ride home after the interview, but if you go in well prepared and have a smile on your face throughout the day, you'll have a lot of positives to take home with you.
Of course, all of this advice might leave your head the second you step into the lobby of an unfamiliar building and prepare to take an elevator 25 floors up, where your immediate destiny awaits. Every company is different, but on-site interviews generally follow a similar pattern wherever you go. The better prepared you are for the overwhelming day, the less you'll beat yourself up if you forget to mention a minute detail of that kick-ass summer internship or you don't actually mention your "biggest weakness" when they ask you, because that would disqualify you from the job.