You need to be level 70, and have your epic flying training.
You get experience by either killing monsters or doing quests.
Probably do daily quests or heroic instances :)
These days, it is easiest just to do the quests in Icecrown to level pretty fast. You can go from level 77 to level 80 in just a few hours if you follow the quests.
The best way is to complete as many quests as possible and by killing as many mobs as you can whilst you do it.
Generally, the quests you do in Brill will lead you to quests in other zones that are good for you as you continue to level up. In this case, Brill quests will lead you to The Sepulcher in Silverpine Forest, which is south of Tirisfal Glades.
What do you mean? You level up by getting experience from killing creatures and doing quests, which you level up with. You just get enough experience to get past level seven! If that's not what you mean, then i don't know. Your character's levels are the only 'Levels' in the game, this is not a game like Mario or something where you have different 'levels' to complete!
There are three ways. You can kill things, you can do quests, and you can do both at the same time
They can be bought in Twilight Highlands once you have completed the first 5 quests or so, the cost various high level engineering items.
The starter zone quests are different for each race. Each race has a starter zone tailored for their race, but this zone usually lasts only until around level 5. After that, they start sharing quests with other races of their faction.
That feature is only active from about level 1-6. It will stop after a little while, just ignore it.
Apparently not, you start at level 1 like most characters (except Death Knights) and you start in your cursed village where you are given quests. Once you get to level 15, you venture into the outside world.
It depends on how hardcore of a gamer you are, it also varies on what class your character is, the area you are trying to level up in and the quests you are doing.