The hostess role
Your duties may include greeting and conversation according to the offer. Ask which procedures apply and where to take questions outside your responsibilities. The job title alone does not mean you should allocate staff, negotiate prices or settle disputes about payment.
The supervisor's role
Organisation differs by venue, so identify the person responsible for shift instructions. Clarify who manages table allocation, breaks and difficult situations. If several people give conflicting directions, ask for a decision from the designated supervisor rather than trying to satisfy every request.
When responsibilities change
An offer of coordination work needs a separate discussion about duties, support, hours and pay. Helping a colleague occasionally is different from becoming responsible for the room. Request a written explanation of the new arrangement before assuming tasks you have not agreed to perform.