I see a lot of work in galleries in which artists have fit hair to Terai Yuki or other figures for which the hair was not made.  Is there an easy way to go about making conforming hair for one figure fit another figure?  Specifically I'm looking to expand the hair collection for TY2.  Any tips/advice/tutorials woul dbe appreciated.

First of all, most hair items are actually just props that load automatically parented to the head of your figure unless they are truely a conforming figure in the Characters library of Poser ending with a CR2 file extension. As Props, to get hair to fit any other figure, all you have to do is load it onto your figure from the Hair library and then adjust the X,Y & Z trans and scale dials until it's in the proper place at the proper size. It's just that simple.

So if the file has the CR2 extension it is a conforming figure? I tried to put Ryan hair on Simon and never got it properly parented. (I have thread detailing my woes somewhere)

If the file is a CR2 it is a true conforming figure built to conform to a specific figure's complete body rigging. You can still used these conforming hairs on other figures, it's just a different process. You load the conforming CR2 hair. Then you have to MANUALLY parent the head body part of the hair to the head body part of the figure you wish to coif. DO NOT CONFORM IT!!! Then it's back to X,Y & Z, Trans and Scale to fit.

 I use the scale, like LostinSpaceman says, but if the head is shaped differently, you can often use magnets and the morph tool to fine tune it. 

I've done that with tons of hairs which don't support V4's headsize morph, which affects the shape of the head, not just the size.

I quickly adjusted a lot of hairs to V4 by picking the A3 version and doing some simple scaling.

It's pretty easy to do the same thing between V4 and M4 too.

Also if you have Morphingclothes you can transfer say an Aiko or Hiro morph over from the base figures. The headsize morph is not accessible in Morphing clothes for some reason, so it won't work there.

I don't like the manual parent method of hair, since the hair won't follow the same way conforming hair does, when you pose the figure.  I prefer actually making a fit that works on the hair when it's conformed. :)

Anyway, just a few cents on the whole thing.

Quote -  The headsize morph is not accessible in Morphing clothes for some reason, so it won't work there.

The HeadSize Morphform changes the scaling of the head and eyes and isn't a morph in the sense that there are deltas used to change the mesh.  

Quote -
The HeadSize Morphform changes the scaling of the head and eyes and isn't a morph in the sense that there are deltas used to change the mesh.  

That would explain why it's not available as a morph... Hairs still need some custom morphing sometimes to match it though..  Probably because the hair may scale differently compared to the head?