Dan suggests asking questions... Part of it is how you ask those questions.
Don't be timid about it... be assertive. Get someone's attention. You don't
want to be waiting around too long.
The people I respect and most enjoy working with are assertive about their
jobs without being dicks. No need to say "excuse me" every time you need to
get by someone... just slip by. I usually just give a gentle nudge (not a
push, just enough to guide the person in the direction I want), or say
something like "watch your back" when walking behind someone who's not
looking. I think people have a tendency to be over-courteous at a new job
since you don't have a rapport with your colleagues yet, and I think in this
case if you do that, you will shoot yourself in the foot by appearing timid
and inexperienced.
Oh, and the main thing... don't be caught standing around, and don't be caught
empty handed.