Tailing--only if the hill is really, really, really steep or really steep 
and really, really long.  (The key here is 3 really's, and keep in mind I 
ride in Colorado and Wyoming).  If it's not a hill that's going to plumb 
tucker your horse out, you'll have a hard time getting back on at the top.  
If you're a featherweight rider you shouldn't bother getting off on the 
uphill.  I get off much more often on the downhill than on the uphill.
Standing--I think is a no-no.  I define standing as putting all your weight 
in the stirups.  However, a balanced two-point, with your center over and 
not forward of the horse's center and your weight distributed from thigh 
through calf is good on the uphill.  Not on the flat.
Posting--Most definately--if you do it right.  Keep your calf on, stay 
centered and balanced and don't use the stirups as weight bearing objects.
Linda Van Ceylon
lvanceylon@vines.colostate.edu
phone:  970-226-1099