Show up on time! Make sure a meeting time and location to begin the day is clearly set. Interpreters should arrive early as a professional courtesy, so the billing duration (as described here) shall only begin at the time the client asked the interpreter to arrive on site.
And pick a professional place to meet. Clients should never ask interpreters to meet them in a hotel room.
Prepare! It goes without saying that you should be well-versed in the subject matter as well as the client's own mission/situation. Don't hesitate to reach out to the client with questions via email, just make sure you cc email@example.com.
No jeans! You are representing Cadence out there in the real world, unless the client says otherwise, let's keep things professional. Equip yourselves with a pen and a notebook.