On airplanes, do you ever wonder how the college-age girl afforded that first-class seat? How about the ill-suited man who nabs the top-floor suite at a hotel?

Some worked the system. To unlock the secrets of free or discounted upgrades for planes, hotel rooms and rental cars, we went to industry experts and frequent travelers. Here are their tips.

Airline upgrades

• Use the upgrade certificates airlines send you for being a frequent flier, or ask friends holding transferable coupons with looming expiration dates to pass them to you.

• Though airlines most frequently award their elite passengers upgrades, it never hurts to be the first in line at the gate counter and inquire about a bump in class. (Ask the gate representative, not the check-in agent.) Depending on the rep's mood and the circumstances, the bump in class could be free or less expensive than if you had originally booked the top-tier seat.

• Alternately, don't be the first to board; hang back in case economy seats are needed and there is extra space in first class.

• If you have a flexible schedule and your flight is overbooked, volunteer to give up your seat if you can get a first-class seat on the next available flight.

• To increase your chances of flying in a higher class, book flights on wide-bodied planes, such as the 747 or 777, which have more first- and business-class seats. Check Seatguru.com (www.seatguru.com) for plane configurations. And request upgrades on flights to destinations with little business traffic, such as Albuquerque, N.M.

Rental car upgrades

• Reserve the rental car location's most popular model (inquire upon booking; most likely it will be an economy Ford). If the car is sold out when you arrive, you probably will receive a free upgrade.

Hotel upgrades

• If you visit a city repeatedly, stay at the same hotel and befriend the staff. Upon check-in, mention that you are a frequent guest and politely ask about an upgrade.

• For a weekend or holiday trip, book a room at a hotel in the business district or one popular with business travelers. The higher-end rooms probably will be empty.

• If you are planning a meeting, family reunion or party, negotiate upgrades as part of the contract.