How do people level up so fast?

Think the fastest/most I did in in one sitting was 1~14x, when I played Mercedes I think. There was a 2x event going on and I bought a 2x card, as well as having a party ready at 110 for LHC. Took about 6hs total? Something like that. The only character I "powerleveled" to 200 was my Dual Blade, which hit 160 in like 2 days (similar conditions), and 19x in 12hs more or so; then I went on a massive hiatus because the party I was SH/HoH'ing with all hit 200 and there weren't a lot of pick-up parties going on when I logged on. Once RLH came around I threw like 30k NX at it and got to 200 pretty easily. Total training/grinding time, probably less than 24hs. Didn't really have fun with the class because I wanted to play my Shadower really badly (it was 194 when I made my DB), but didn't want to fork over the 40k NX needed to xfer the gear back and forth every time...

When I make new characters (which is rare, but happens) I generally follow this training route:

10~30: Mixed Golems
30~40: CDs at KC Square, or the mixed Cellions map in Orbis if the class has really good vertical mobility
40~60: Twisted Jesters, usually Toy Room
60~7x: Iron Mutae (B-1), Aliens (Corridor 5/6) if the class is OP as balls
7x~110: Aliens (Corridors 5/6)
110~165: LHC (usually with guildies who can destroy the spawn fast)
165~170: Random KSH map, usually the 2nd map (Pirate mobs)
170+: Hall of Honor

Some of the areas are less than ideal for the level but I find that most of the new classes are ridiculously strong without funding anyway, and can handle the maps pretty easily. 2x helps a lot.

Also I made an Angelic Buster and hit 106 on the initial day without 2x, only using those (free) 1.5x cards. Took like not even 4hs or something, class is retardedly strong.