Hi, commander..

1. You don't need to parent the cloth to the figure. That's only needed if you decide to save the prop to the library (and if you want it to automatically go to the correct position when you re-load it from  the library - see extra notes below).

2. Try the following... (assuming you modelled your poncho as a flat cloth - definitely recommended)..
    Start a new Poser session.
    Load your figure and zero it (not the default position, the zero pose).
    Import the (flat) poncho.
    Position it (if necessary) such that it is above the shoulders, but below the chin.
    Ensure that the pocho is NOT intersecting with the figure  anywhere.
    Scale it in x and z if necessary.
    (SAVE as PZ3) - just in case you need to restart..

 Enter the cloth room, clothify  the poncho, collide against your figure, (DON'T bother with any "drape frames", they just get in the way, set them to zero).
 Run the sim. (30 frames should be more than enough..)

Assuming that worked -
 Find the best (most natural for a zero-posed figure, cloth falling naturally) frame of the sim, and export the cloth as .obj. (under new name - eg: PonchoDraped). DON'T CHECK ANYTHING ON EXPORT.
 Exit Poser (to free up memory, mostly), and restart it.
 Load Figure (and zeroise it).
 Load PonchDraped (DON'T CHECK ANYTHING ON IMPORT).
 The Poncho should now fit the figure in the "zeroised" position. All the above is, really, the easiest way to get to a starting position. Once you get used to using it, it becomes second nature..

At this point, if you think you're going to use the poncho again, you could parent it and save it to the props library. (BTW - What parenting does is move the prop (ie Poncho) to the correct position on the figure when loaded from the library, and moves the prop together with the figure if you move the figure in the studio. There are other effects don't affect this discussion, except to say that if the pose moves the figure, then parenting can get in the way of the cloth moving correctly..)

OK. You have figure (in zero position) and fitting Poncho.
Next...
 Go to frame 15 - 20 (it depends, 15 is probably more than enough for a poncho) and pose the figure.
 Return to frame 1 (not absolutely necessary, but avoids confusion).
 back to Cloth Room, clothify PonchoDraped, collide against figure etc and let it rip...

Anyway, that's the way I do it..... there's probably a better method but I haven't found it yet.
Not that I've looked too hard - it works for me, doesn't cause me much trouble, so unless someone comes up wit a super-streamlined approach I'll keep using it..
 
Hope that helps,

Cheers,
Diolma