You must take off your shoes. → Your shoes must be taken off.
He shouldn't smoke cigarettes in this room. → Cigarettes shouldn't be smoked in this room.
We could see Tom in the crowd. → Tom could be seen in the crowd.
Eddie might help you if you ask him. → You might be helped (by Eddie) if you ask him.
We can order some lemonade at the bar. → Some lemonade can be ordered at the bar.
We have to protect our sea. → Our sea has to be protected.
They ought to park the car in the right place. → The car ought to be parked in the right place.
You should speak English in class. → English should be spoken in class.
Mary used to keep a dog. → A dog used to be kept by Mary. (Less common in passive voice)
People would buy tickets at this booth. → Tickets would be bought at this booth.
They can book rooms in advance. → Rooms can be booked in advance.
We may borrow his car for a day. → His car may be borrowed (by us) for a day.