Clarify the company dress code in advance.
Note as much as possible about the environment, such as the other workers, the manner in which interactions with co-workers and customers occur and the general pace.
Ask questions to clarify what you are observing and to learn more about the professional’s career progression. Transition times are often ideal for these conversations.
Be sure to ask the professional if any of the information you learn or observe is confidential (trade secrets, etc.), and respect that confidentiality.