My two cents:

Backstab the highest tier creature you can, not necessarily something you could dance with
Use LE only, no penalty on your backstab and less roundtime
Ambush sight, it helps you overcome perception and teaches backstab as well
If learning is slow because your ranks are getting higher, use shadowstep to quicken engagement

>>So stabbing eyes is better exp than chests, etc.?

Yes this is correct. If you are training on quadrupeds then the best way to do it is to aim for the eyes/head/neck. Or the hardest body part you can hit while still passing the ambush check. (Not getting the "You failed to surprise the target" message)

I'm not sure if this works better than attacking a hard to hit part, but what I do is I attack limbs. I attack the right arm until I take it off, then the left arm, etc. From what I understand each limb has the same health as the torso, and exp is based on the amount of damage you do, so each time you remove a limb it's the same exp as if you had killed the critter. Maybe it depends on your skill vs the critter, but at 600 ranks I find this teaches better for me than aiming for an eye.