You will get so mich **** these days if you think you can have a carry on for up above, and something below by your feet, and a suit bag (I got a way with it but I was prepared to put suit bag in carry on but didn't want wrinkles, you could wait till you are about to board to consolidate the two bags, then when you're on the gangplank take it out while people file past, once you get to the cabin it's too late for them to quibble about the suitbag and your carryon suitcase and your other bag)
Hand your suit in the bathroom while you shower to help with wrinkles
I got a suitbag on Amazon for cheap, it was GREAT
Also a bag for shoes, it has a divider inside so your leather shoes can't rub on each other and scuff them up, I didn't like the idea of my dress shoes with snow salt floating loose in my carry on suitcase
Be sure anything you *truly* need comes on the plane with you, don't gatecheck, none of that horse**** where they can lose your bag
Always have a professional appearing portfolio thingie (mine was $15) that will hold your own app for review (I forgot the year when I did X, made me look dumb but I can't memorize all my life details) as well as a pad of paper for you to jot things down, you'll look sharp when they ask you if you have questions and you open that thing full of handwritten intelligent q's and start taking notes)
Try to remember something specific about your interview with someone to refer to in your thank you note so it's less generic, I wrote mine right after interview, another reason to have the pad above for notes
They sell black safety pins, always good to have a few on you in a pocket if any buttons go
Neutrogena face soap is a bar so it doesn't count towards your liquid allocation on planes, look for anything you can get in dry form and add water like that for conservation, I stayed in some **** hotel that didn't have shampoo in the room and it was after hours, you can use bar soap in a pinch for hair, facewipes with make up remover for example won't count for liquid, Listerine strips, for example
You can get away with having toothpaste and chapstick and lipstick and masacara and stuff like that separate from your liquid bag and they won't catch in if it's thick like that, especially if it's scattered amongst your things
I bought a pad of concealer like Boing! since it didn't count as liquid, and it forced me to go light, you don't need a mask of liquid foundation day of
Go nuts with small containers to bring a pinch of this gel and that liquid if you needs lots of stuff like that, make sure it's in an extra bag and can't leak onto your suit
Neutrogena spot zit stuff in a small orange tube you really do see results from in less that 24 hrs, anything bothersome I could spot treat the night before interview
I did like 20 or so interviews in a month without ever coming home, I have some ideas on how to live on the road, PM me for other travel ideas
If you can keep some floss or toothpick or those little combo thingies +/- mirror on you to get any after continental breakfast/lunch out of your teeth, nothing like needing floss and having none
Definitely see to your oral hygeine and have breath mints, nothing like halitosis to make an impression
I also had every PRN you can imagine handy, nothing like overnight flu/cold/sore throat/diarrhea (I caught legit laryngitis on the plane, boy was I glad I had Theraflu, the office gave me hot water and thought I was a badass drinking that down interview day)
Just the more unusual things that came to mind
Check my post in a thread about what interns should have in a bag for other nicety ideas