First: Find out the lowest “published” Business or First Class fare on your route.

For years we were trained to look here last because fares were sky high. But now, with fares falling in more domestic markets by the day, start here first.

How? Ask a reservationist for the lowest Business Class or First Class fare—in your specific market. Then try to work around the restrictions if there are any.

This is critical. Don’t start with your exact dates, if you can help it. Start with the dates that will give you the lowest fare. If you can adjust your dates slightly you’ll often find a fare you might otherwise miss (and you’d never know it existed if you didn’t ask for the lowest fare that exists). Even adjusting the time of day you depart can make a big difference. Asking a travel agent is preferable, since they can scan most airlines’ premium fares at once; or ask an airline reservationist, though they’ll usually only give you the carrier’s fares.

Ask them to look for Y-UP fares, a full coach fare with a free upgrade to the next class of service, and for A, D, I, or Z fare-basis codes (don’t worry, they’ll know what you’re talking about), which are heavily discounted Business and First Class (see chart on page 3 for specifics).

Tip II: Then ask about “alternative” airports (i.e. Newark instead of JFK or LaGuardia; Burbank, John Wayne, or Ontario instead of LAX). These airports often yield far lower premium cabin fares. If for no other reason, availability might be better.

Now you’ll know the airfare(s) that your mileage or elite upgrade program must improve on.

Second: If you’re an elite member, determine the best fare that also allows you to confirm an elite upgrade (if you’re really serious) at time of ticketing.

Third: Rank the fares you have against redeeming miles for an upgrade.

Domestically, a mileage award for a premium seat is usually only of great value on long-haul routes and/or when a heavily discounted First Class fare isn’t in the market, and upgradeable economy is very high too.

Fourth: Weigh the costs in terms of the best value.

A low, confirmed First Class fare takes chance out of the equation, and will earn extra miles. A mileage upgrade can be a good idea if you have the miles to burn, but otherwise they’re usually best saved for international flights. And remember, when all else fails, United’s Ameniti.com 2-for-1 program can at least cut a domestic full-fare in half.