I never found a GOOD joint rolling guide. There seems to be no right set of words that can give you the ability to work your fingers just the right way. Watch friends roll, and practice a bunch, those are the best two ways to learn. Also letting friends watch you, they may notice an inefficiency in your technique, like put index finger here instead of here.

Anyways... here is a my best attempt at a "how to" on a cone.

1. Place broken up weed in joint
Code: 
    +-------------------+
    |                           |
    |    oOoOoOoOoO     |   oOo = weed
    |                           |
    +-------------------+
I'm right handed, don't know if all right handed people will find this the easiest way, obviously change method if needed.


Fold in half and hold like this

Code: 
   +-----------------+
   |    oOoOoOoOo    |
   +-----------------+
          ^       ^
          L        R
Pinch with your thumbs toward you. Your left thumb where the L is and right thumb where R is. The weed is inside the fold so you won't see it, but I put it in you know where to put your thumbs.

Start rolling and tipping clockwise. Your right thumb will keep the weed from falling out the bottom. The left thumb is used to start to shape the weed to make the cone. When things are sort of shaped, carefully tuck the paper at the right thumbs position and twist off the end keeping the left thumb in place. With the end twisted and coned, you whould be able to lick the full length of the gum and roll the rest super tight. The open end should easily be large enough for a pen to fit in and compact the weed.

Hopefully this helps and isn't totally confusing. Good luck!