With the economy on screech and carriers having smartened up by cutting capacity rather than prices, forget about free upgrades other than at odd hours on odd routes (which some may have the luck to require).

The advice above is the best. If you are flying for business and are twisting yourself into a pretzel to earn tickets and upgrades, it is not likely worth it.

Rather than worrying about hoping that the guy in front of you on the UG list drops dead, take a look at B6 Mint for the TCON. If you do some comparison shopping, you will likely figure out that you are risking a middle seat in Y near the lav just to get a "free" bag.