Last Updated May 18, 2010 10:00 AM EDT
But there are a few other, less-obvious tips you should bear in mind if you want to snag those free upgrades.
Last week, Clever Dude listed 10 tips for getting free airline upgrades. And while most of them are nothing new to seasoned, frequent business travelers like yourselves, a few of them seemed well worth mentioning.
Subscribe to the airline newsletter. Who needs another piece of junk mail? Well, don't think of the newsletter as spam -- consider it a way to get a head's up about special deals and bonuses for booking flights during specific blocks of dates or to certain cities.
Look for promotional codes. Some airlines use special "Y-Up" and "Q-Up" codes. These codes are designed for regular business travelers whom the airlines wanted to reward outside of their traditional frequent flyer program. You pay for a regular coach fare, but your flight is booked into first class. When shopping for flights online, look for ticket numbers that begin with QUP or YUP.
Check in early or late. You know the old rule about just asking for a free upgrade? It doesn't pay off very often, but it stands a better chance of working if you don't check in with the herd -- If the airline has an upgrade to give away, they may do it early to avoid last-minute shuffles. Or if you check in late, you stand a better chance that all the coach seats have been filled, so you may get booked directly to first-class.