A good question.
A local answer.

Read recent branch-level reviews and photograph the car at pickup and return rather than choosing on headline price alone.

Ask the rental desk about tolls and the easiest legal exit from its garage; the route out matters more than the short walk in.

Check current encounter schedules and accessibility before buying tickets, then leave enough of the day for another city activity.

Compare walking, light rail, train and ferry combinations by door-to-door time rather than the number of stops.

Confirm the bridge activity finish time, luggage collection and White Bay transfer together; the terminal is not at Circular Quay.

Compare an independent train day in the Blue Mountains with a tour by total time, walking and the stops you most want.

Choose the viewing spot first, then look for a takeaway shop within a short walk so the food is still hot.

Ask the hotel whether it will hold bags after checkout and for how long, including any fee.

Leave one unscheduled day for weather, especially if both coast and mountains are important to the trip.

Compare set-menu price, arrival time, minimum spend and cancellation terms before paying a deposit.

Do not assume every bar or restaurant closes; confirm individual opening times and any public-holiday surcharge before setting out.

Verify cancellation and payment terms with the operator and seek recent independent reviews for that specific itinerary.