If you are dead serious about getting an upgrade for "free", these are the strategies that you need to know. It may not guarantee an instant upgrade but sure it will work in one of your future flights.

It won't hurt to ask. Just do it in a polite and direct way. It's actually as simple as saying "If you are upgrading passengers on this flight, I would like to be considered." You may not be considered but at least you tried. It's just like planting an idea into their mind and if there's indeed an upgrade, chances are they'll remember and consider you.

Be friendly to the staff and ground crews. Address them in their name. That's the purpose of the name badge in their uniforms. It will create a more personal connection and uplift their morale. In return, they will give you back the favor if there's an opportunity. An airline upgrade is more likely one of them.

A good timing can do its tricks as well. Being on time or reasonably early for check-in would give you a better chance of getting an upgrade. Have the courtesy of making a request when there's still ample time to spare before the flight.

Be reasonable instead of being demanding. If you're too demeaning, your chances of being chosen for an upgrade if the opportunity arises will be slim.

If the flight is full, you have a better chance of getting an upgrade. Airlines normally oversell seats on a flight and it won't do them harm if people need to be upgraded to accommodate everybody on the flight. In this case, you may be lucky to be the one.

Be willing to give up your seat if the flight is oversold. Sometimes they need your seat to accommodate a family traveling together.

When this happens, they usually offer an upgrade for the inconvenience. Just so you won't get frustrated. Now that you know the strategies, you have a better chance of getting an airline upgrade the next time you travel.