One thing that came to mind that I wanted to mention is over-familiarity. In today's more casual society, sometimes we tend to assume that a seemingly less hierarchical work environment or even one when, say, partners seem young and hip and not stiff, means that we can really let our hair down, speak as if we are speaking to our pals, and even joke in a way that we think is funny but might actually offend. Case in point: my friend, we will call her Partner Jennifer, had to leave for an appointment. She ran into junior associate Ellen. They briefly discussed something and then when Ellen saw Jennifer was leaving, Ellen made a comment about "oh I guess you don't have a lot of work to do since you get to leave early." Or something to that effect. Similar thing happened to another person I know. Jennifer - who is a youngish, approachable partner - was really annoyed. First, Ellen has no idea where Jennifer is going. Jennifer may be off to a client meeting. Second, Jennifer has 15 years of experience, including long nights, weekends, holiday work. Jennifer has busted her tush and is entitled to respect, particularly from junior attorneys. Even if Jennifer is going home - that really is not for Ellen to comment on. Ellen hasn't even proven herself yet.
Thus the long and short of it is to remember - and I know I've mentioned this before - these people are not your pals. They may seem approachable and laid back but there is still a hierarchy and you need to respect that. Be careful how casual your conversations may be. Watch the "digs," and watch the casual language - cursing, rough slang, etc. I've been in interviews where people throw out the F-bomb as if it is a "hello." This gets you marked way down - actually off totally - in my book. It is about judgment. These days, we are very sensitive to judgment red flags. Remember it is a buyer's market now. Show us your terrific work, your potential client handling skills. Keep the slang and snide comments for another day.