The OP should also be aware that there are basically TWO types of miles you earn for flying: redeemable miles (RDMs) and elite qualifying miles (EQMs, aka "status miles," MQMs, etc.). Generally, for flying, you earn both at the same time, though not necessarily in equal quantities.

The frequent flyer game is much more complex than just earning miles (RDMs) that you can redeem for awards (including, but not limited to, flight awards). The game as played by FlyerTalkers often involves looking for ways (such as via "mileage runs," special EQM promos, etc.) to gain elite status of some form, which then enables you to earn extra bonus RDMs on flights, upgrades, and a host of other perks. The ability to upgrade to a nicer class of service while having paid for a cheap economy class ticket is something that is highly prized in these parts.