This advice is fairly generic to "How do I stat NPCs in a system I don't know" to a large extent.

1. Steal I: Look at stats for NPCs in campaign examples, see how they glue together, pick them apart, run them though some dice rolls, work out what you'd be missing if you were a player.

2. Steal II: Look at the writeups for campaigns on the internet, char sheets if they've got them, use them as seeds for initial characters.

3. Ask: Put up some questions here about how you'd stat effective exalted characters. Or, if not here, a dedicated exalted site or forum of some kind.

4. Play: Don't, to start with. If your players are as new to the game as you are, they're going to be finding their feet with effective uses of the stuff they've got too, and you've got the advantage of being able to iterate over builds that don't quite work (if you accidentally build something overpowered, make it stupid. A +52 level sorcerer is much less of a challenge if they can't count to four, after all)

5. Read: Start from things like this:

   • http://rathess.xi.co.nz/exalted/index.php/Exalted_208_Practical_Charm_Building
   • http://www.bazzalisk.org/ (Character sheet examples abound)
   • http://exalted.xi.co.nz/wiki/Main_Page (a wiki)
   • http://forum.rpg.net/showthread.php?t=28407 ("Send your Cool Exalted Characters")

Sorry I can't be more specific, though :(

It's a tricky question to answer, because the Exalted metaplot ends at a specific time, and that specific end time hasn't changed since the 1e corebook. A few products have extended the Exalted timeline -- "Return of the Scarlet Empress" is the latest to do so -- but these generally provide possible futures. The First and Forsaken Lion doesn't necessarily conquer Autochthonia, the Sidereals don't necessarily unleash the Kukla, the Scarlet Empress doesn't necessarily enact a plot to render Creation and Hell one and the same.

What the Exalted metaplot has mostly been, then, is background. Setting elements that were implied to be X in a brief mention in an early sourcebook were expanded at length and revealed to be Y. Characters, power groups, whole regions were unveiled as unexpectedly awesome and tied to other setting elements in unexpected ways: the Haslanti League, like Halta, was a Lunar experiment. A Gold Faction Sidereal might share an office in Heaven with a Bronze Faction Sidereal. Astrology works along different principles than one might expect. The floating mountain in the far East isn't full of upsy-daisium, it's a derelict flying war machine.

Thus, there isn't a single good source to follow, because there isn't a single narrative throughline. The 2e core book hits a lot of the high points accreted over the course of the first edition, but it's presented as setting, not metaplot.