Not sure where to post this so forgive me if it in the wrong place.....

I have a moderate grasp on what an upgrade is but I'm not exactly sure how to get them.

1)Other than purchasing upgrades directly from the airline are there any other ways to obtain them?

2)Are upgrades transferrable?

3)Is a 500 mile upgrade not good for say a 750 mile segment? Would you need to use 2 "500 mile" upgrades for a 750 mile segment?

4)Does each upgrade bump you up to the next higher class of service or to first class? (economy upgrade to business, etc?)

5)How much does a typical 500 mile upgrade cost?

6)How much time before a flight can you request to use an upgrade?

7)Is there such a thing as a courtesy upgrade at the gate if there is room in a higher level of service and if so...how do you approach this?

That's it for now. THANKS IN ADVANCE!!!