I still didn't have a clicker so I'm using a very enthusiastic "GOOD Girl!!!" as the marker and lo' and behold, I taught her to shake her head "no" in two TEN minute sessions over TWO days!
I'm really excited! She's a really smart cookie (for instance, if I'm doing a serpentine with her and we've done it a few times I can drop the reins and she'll just do it perfectly on her own without any input from me) and I've been trying for the last year to figure out how to get her to put all that smartness to good use.
I just bought a clicker so that should help too. I'm really excited! I've always wanted a pony that did tricks! Haha
Maybe I'll teach her to put her ears forward on command so she looks less angry in pictures. Haha