I'm sure this advice applies to any type of internship, but bring to the internship a high level of professionalism and be pro-activ(e and pimple free). Depending on the type of firm you'll be working with, be prepared to work with some terrible clients (see: horribly rich, horribly snobby, terrible taste). If you're going to be primarily drafting, perhaps you should refresh your memory on autocad/archicad/revit etc. if you haven't used it in a while.

Also, wear black cardigans. And be as hip as possible haha

Be prepared to spend hours working on models and drawings just to have your supervisor change their mind and have you redo them.

ask questions...dont sit and think forever when you get stumped...

be first to arrive everyday. last to leave. enjoy what you do. don't complain. ask many questions. forget the beach.

Be enthusiastic and pleasant.

Don't tell anyone else in your class you get a job, let alone a paying job. Unless you want to get beaten up behind the old barn after school.

*but feel free to tell all your non-arch friends about said paid job, especially if they've been working for 'school credit' at a non-profit.

Definitely don't tell your friends. I almost kicked the crap out of a really close friend of five years when he posted "I GOT A GREAT JOB, STARTING RIGHT AFTER GRADUATION!" as his AIM away. He's also trekking around Europe for a month, on parent's money. Must be nice...

before you get there:
reearch the firm - see what they do and understand it if possible
make sure your wardrobe is ready - jeans are ok for students in some firms, not others
brush up on the skills they should expect (especially 3D or AutoCAD if mentioned in interview)

after you get there:
be professional (clothes/omn-time/attitude, etc)
make friends (best networking possible)
listen to everything (even when its obviosly BS)
ask questions ALL the time
DO NOT facebook/myspace/twitter on company time or equipment
DO NOT take long lunches
Ask your supervisor what his/her expectations are and ask if you can assist with anything extra
NEVER turn down a learning opportunity (lunch&learns/webinars/AIA meetings, etc)
HAVE FUN !

^ wow, I am 0/9 on that list. HA!

10. don't hesitate to come in on a Sunday, wearing flip-flops and an offensive (but funny) t-shirt. Then have the model you're building take all night into Monday, and wind up being stranded at the office because you live 90 minutes away, with nothing to change into but that same set of flip flops and dirty t-shirt. You get the best looks from principals that way. Oh, and forget your toothbrush and deodorant. Coffee covers all bad smells, right?