At Xform, we always ask for a proper motivational mail, an up-to-date C.V. and, most importantly, relevant and accessible portolio work. So don't call us and expect to be hired at the end of the conversation. And don't let your school do all the work for you either!
The mail should be a short introduction to you and what you do. Why are you applying at Xform and not some other company? What is your goal after you finish your education? If it isn't landing a job in gamedevelopment, don't bother; internships are scarce as is!
It's always good to have previous fulltime work experience. Even if it isn't in the games-industry. So be sure to list everything on your C.V. All information should be good (providing an incorrect telephone number doesn't make a good first impression). Please state if you're a boy or a girl (to avoid emberassing situations)!
Have a place on the web to display your work. It should be easy to navigate and it should work, doesn't matter if it's your own fancy website or a personal space on a community site. Make sure that the stuff you show is good enough and works (even though that might limit quantity). If you've worked on a lot of team-efforts, make clear what your attribution was. And please: have a proper non-idiotic email address.
Okay, so we want to meet you in person. Be on time. We really appreciate nice color prints of your work. Also, don't hesitate to bring crappy older work. It can give us a good idea of where you started out from and how fast you learn. If you really need to bring a notebook, make sure the battery is full and you have the stuff you want to show ready (and tested!). Don't worry too much about things we might ask. It's all about getting a good idea if someone fits in the team or not.
At least try to make an effort not to come across as a total moron. Unless of course, if you ARE a total moron. Then it's good that we get an honest early warning.
The most important thing is that you get a good impression of what working at Xform is about. We usually give a small tour and an impression of what we're working on and how we do it. Remember, it could be the place you'll be spending a lot of time, so don't hesitate to ask if you're curious. Please let us know if you have special needs or diseases! Don't think you'll surprise us though ;).
Can't wait for your mail!