Printed or Digital Portfolio?
The right answer would be, in my opinion, both.
A good digital portfolio is an excellent choice when you need to show it to companies you don't have immediate access to, such as when applying and sending out your resumé and other personal information, to later on narrow it down and choose the ones they are going to interview.
deviantART has now a lovely portfolio option, with a very clean and minimal design, with a space where you can write a few words about you and your work. There are also other websites you can try and that allows you to have free accounts and lots of customizable opitions such as viewbook.com.
You can also design your own, and save it as a PDF. Some companies prefer this one actually, as it is easier to access ( usually burnt on a cd ) and can be sent out by mail. Make sure you make it clean looking and minimal.
Your printed or physical portfolio as you prefer should be for when you are face to face with the interviewer so he can take a look at your work, and ask you questions about your technique and concepts. Don't make it to extense, if they have had previous contact with your digital portfolio, make it so it has around 10 examples or less. But try to give them examples to all kinds of work you can do, the most varied it is the best, this will be proof of your creativity, versatility and ability to adapt yourself to different styles.
Know your audience
As a graphic designer I have basically dealt with it all. Different companies have different "personalities". I have been to extremely formal places where they seem to have a stick up their bum, and I've been to very down to earth and laid back places where they even smoke pot at the office. Before you go to an interview or organize your portfolio for a specific company, don't forget to do your homework.
Try to find out and really study the company you have applied to, as much as you can. ( This happens because sometimes you send out several resumés, having just contact with the fact they want to hire someone and give away their contact )
It's a very uncomfortable and awful feeling when they ask you "Why would you like to work with us?" or "Why do you think you're right for this job?" and you have no idea what to say.. I know I rehearse these at home everytime :] If you have a prepared, clear and informed answer, you are half way there.
What to wear... what to wear?
And if you think the only ones who should worry about this matter are the girls.. boy, you couldn't be more wrong... As I have mentioned before "image" is the only way you have to get to them and I personally believe that first impressions DO count. If you have done your homework and studied the company you're going to, then you will know what kind of clothes you should wear. I usually choose something in between, I dont wanna look too confident and laid back, and if I wear something too formal I won't be able to be comfortable while they ask me all the questions. I know this because once I wore a blouse that was a size below mine ( I kinda bought it in a hurry, don't ask haha ) and I couldnt breathe the whole time. Nice huh?
Come on, who doesn't get nervous when being interviewed. It's a normal thing, but that doesn't give you an excuse to chew a gum while you're at it! One of the things that is harder for me to control is my hands. Just like when I'm teaching classes, or at a palestre, my hands are all over the place, and you can avoid this by using a pen to play with. This will calm down your movements and make them more natural.
Try to keep your hands at sight, don't hide them on your lap or cross your arms, for that can show insecurity. You want to be strong and open, honest about your questions. If you are being interviewed by more than one person, keep the eye contact with all of them, shifting as you speak in a calm natural way. Usually there's always one that talks the most, but don't be fooled and ignore the others, they are all judging you.
Hope it helps somehow, please if you have any guidelines and tips of your own share them in a comment, don't be rude. Thank you.