What is the most effective way to get upgraded on flights without paying business fare?

When a flight is over sold and they solicit volunteers, you can request an upgrade instead of compensation. Doesn't mean you will get it, but you can always ask. If you are talking coach to business on International its even more unlikely.

If you fly a lot, be a member of the airlines frequent flier program. Medallions are the first to get free upgrades, the more you fly, the better your chances of upgrades are.

The ONLY time someone will be upgraded is if all the medallions have been upgraded and coach is still oversold and First or Business is still available is first, a full fare gets upgraded, then if we have to pull random people it will be someone sitting close to the counter that is dressed appropriately and doesnt beg for it.

People booking coach always want something for nothing. If you want a better class of service, be willing to pay for it. There is no obligation to fill those seats. The discounted coach fares dont come close to the price of a business or first class seat. So if you want something, either be loyal and earn it, or pay for it.

I'm told that volunteering to take the next flight when the flight was overbooked is the best way to get a free upgrade. Just make sure that you can get what you want before you volunteer.

Assuming you are eligible for free upgrades, your chances of being upgraded is better if you take a plane with a big first/business class section, crowded coach section, and flying at a time when few business travelers fly.

1) Use your miles to upgrade only

2) If you fly a certain # of miles the airlines have clubs/status you will qualify for. Based on your status you will qualify for free upgrades.

Check with the airlines for specifics on their programs