The best method is doing it an external program, such as Zbrush. Someone (Dodger, maybe?) suggested making the face morph three times, then combining them (as three separate dials in Poser), in order to get the most realistic results.

The easiest method is dial-spinning. In addition to the DAZ morphs, I use the Brom and M3 Head Sculpture morph packs (brokered at DAZ). However, re-distributing the custom morph becomes a problem then.

You can also combine the methods, mixing some custom morphs with the dials.

One thing - no matter how good your morph is, it won't look right without the right texture. (That's the advantage of the Face Room, or Facegen - it creates a custom texture from photos, to go with the morphs.) Choose your texture carefully.