It's always nice to get something for nothing. When it's an upgrade to business or first class air travel, you can do your bit to help it happen, advises Keith Burton of the Association of British Travel Agents:

Join a frequent flyer program. Airlines only upgrade because they have to (they over-book, calculating that some people won't turn up). They will always choose their most valued customers first.

Ask if the flight is full when you check in. Say that if they're looking to upgrade, you'd like to be considered. Don't be pushy.

Dress smartly. The airline won't want to upset (fare-paying) first lass passengers by seating them next to a scruffy backpacker.

Travel alone. You'll be easier to seat than a couple or group.

Don't be first at the gate. Staff won't want to hold up the queue and won't know yet which seats are free.