Before getting your hopes up, know that free upgrades are rarer than ever these days. That said, you’re most likely to get lucky on oversold flights, when agents are trying to find seats for the displaced masses.

Vacant first- or business-class seats are initially made available at the gate to travelers upgrading by either paying or using frequent-flier miles.

Next in line: savvy fingers-crossed folks. “The most valuable person in this situation is the gate agent,” says Kathy Sudeikis, president of the American Society of Travel Agents. “Looking the part is important, shmoozing is important, and being gracious is important.”

Connect with the agent by “being truly interested in that person,” suggests Travel Channel chief correspondent Peter Greenberg. Ideally, after hitting it off, you won’t need to ask. If you do, subtlety is important, says Greenberg: Using the word upgrade is “the surest way not to get one.” Try something like “Are you full up front?”

Then open with personal information before making a request, Sudeikis suggests: “We’re celebrating a special occasion. If you need to put anyone in the front of the plane, may we be considered?”

Finally, if you hear travelers unsuccessfully trying to upgrade, don’t bother turning on the charm, she advises; resign yourself to getting comfy in coach.