You might be wondering what you should show up on your first day with. Well, I think you could ask the recruiting coordinator in advance if there are specific things he/she wants you to bring (hey guys and gals, did you see I said he/she...yippee!!). Anyway, I would bring (1) yourself, of course, properly attired; (2) perhaps a briefcase or other appropriate business-like looking bag; (3) if you like, a portfolio with notepad (4) a couple pens (5) your cell phone -- you don't want to use firm phones for long distance and some calls that seem "local" but under firm's plan are not -- they will require a code and your cell is cheaper; (6) identification cards for work eligibility, pretty much all employers will require this -- check in advance, as I mentioned before and get your docs out; (7) usual stuff you would have of course such as wallet, etc. (I assume that is obvious but I throw it out anyway).
When you arrive, you will usually be greeted by the recruiting assistant, or office administator or your advisor - well, someone involved in the program. In BigLAW firms, you will usually have a formal orientation program with an agenda laid out. Make sure you do not set up outside lunch plans (with friends, etc) as the firm usually wants to send you out to lunch (often with your paired associate or other advisor). Take a look at the agenda so you can familiarize yourself with whom you are meeting. Keep your phone on silent or vibrate so it is not ringing away with calls from friends while you are in your meetings. Tell your friends and fam that you will be tied up most of the day and you will report back later.
You will be meeting lots of new people and it can be overwhelming. At least learn your assistant's name and make sure you greet them each day. They can be your best friend in the firm because they usually know more than a lot of the lawyers. And, usually firms will assign the very experienced assistants to the summers. If they make suggestions, listen. Say please, say thank you. If you are going to be in a meeting for a while or out of the office say, watching a deposition, let them know and let them know how to reach you. Remember, they can look out for you, but they will also let someone know if you are an a-hole. We listen - we don't believe everything, but if I hear about rudeness to staff, especially from more than one -- I do listen and it can be a factor.
Also, regarding your associate advisor, yes, he/she (see - I did it again, HP really getting PC!) can also be a great source of information and guidance. BUT, do not confuse advisor with your wife/husband/partner (PC Alert!) or best friend. They frequently sit in meetings with the hiring partner and may discuss things you've said - like you said "I hated working with Joe." Well, if Joe's group is only group hiring, that may be a problem.
How did I do? Did post properly address concerns of female and male readers? C'mon all, it's not ALL about gender. Sometimes it is just about the workplace, working hard, doing a great job, and showing everyone what a fabulous lawyer you are or can be. I'm just trying to get you off to a good start, the rest is up to you. :)