Ask when you place your order over the phone or check your in room menu. Don't tip twice. Several years ago their were no reserved seats in any showroom. However today, many showrooms have seating location numbers printed right on your ticket. If so, there is no real reason to tip the usher much for that service.
Ticket reservationists - Nothing.
Valet Parking - Parking is generally FREE at most Las Vegas hotels. Less if service hasn't met with your expectations. All Rights Reserved.