Just drop it into D, and have at it...play power chords, and little cool riffy thingys and your set...
Mesa Dual Rec/ Mesa 4X12 cab
01 PRS Custom 22
06 PRS Singlecut Ann.
1965 Fender Mustang
Ibanez acoustic
AceFrehley Epiphone LP
Takamine Explorer
tr-2 tu-2 / EHX DMM / MXR Script Phase 90 / SMM w/ HAZR
WH-1 Whammy / 535Q Crybaby
don't forget to hate your parents. that's important.
fender showmaster=$650
fender FM65=$200ish
digitech RP200a=$100
sucking at guitar no matter what=priceless
wat does drop d mean? or drop c? or something like that
moving for the sake of motion
finds tabs for some of your favorite songs, you'll find it's mostly power tabs and such. Play some of them
Drop (or 'dropped') D is when you tune your low E string down to a D (DADGBd); Drop C is technically when you tune the E down to a C, but usually people mean to tune to dropped D and then down another whole step (CGCFAD).

Mostly emo and hardcore bands use minor scales and tonalities, and power chords.
Play random powerchords in drop d or drop C, or raise g (lowest string is G, above E) and scream random words about how you hate life and how your girlfriend took everything away from you.
You could try powechords but those are so bloody simple, you probably already know em anyways. Try learning songs by Between The Buried And Me or Poison The Well, they are not emo (maybe a tiny bit) but if you learn that kind of hardcore style it can easily be applied to emo music. Most of BTBAM's stuff is pretty technical and difficult/challenging. Give it a go.
Threadstarter, I'd advise you to learn what real emo is. Poison the well are more emo than hawthorne heights. Crap like the used and my chemical romance are nothing like emo.

But for real emo guitar: Learn to love octaves. Most emo bands have more than one guitarist so harmonizing leads are also common. Barre chords are common but frequently try and add notes to color the chord more making a more complex sound. There are no particular chords or scales you can refer to, emo or post-hardcore as I'm now going to refer to it, is an extremely vast genre with my different styles in it. Just go with the key of the song though most bands stay within the major and especially minor scales there is nothing you have to follow. And make use of as many different channels and effects as you can, since it's such a diverse genre you can use a lot of sounds.

If you want to specify which kind of post-hardcore specifically I can go into more details on how to emulate that sound.. (and please don't let it be generic mtvmo)
yeah its easy, or if you would like something more complicated like atreyu or bullet for my valentine, try just some of their songs, then youll get inspiration
or at least that works for me...