I trained my girl to rear on command (though many will say that is a bad trick to teach). I start off with making her work a bit to get her 'excited', then calm her down into 'thinking' mode so that she now knows that she's about to learn something, or do something she's not used to. Then, I'll move out in front of her a bit and ask her to walk, then (and not in a 'snappy) way) I spread my arms and walk towards her saying "UP!" firmly. She is very good but is still a little new to it, so sometimes she'll get confused. When that happens, I do what she gets confused with over and over, then mix in the rear, then the confusion part, and withing 5 minutes, she knows the difference between what she 'thinks' is a rear command, and what actually IS a rear command. I only do this on the ground as well, and in an open place so she doesn't feel trapped or frightened or anything like that. She used to jump sideways at first, but simply jumping WITH her, made her understand that she was to rear in place, and not just go sideways lol. Now, she loves it though, and it's her favorite trick! My next trick is to bow though, so that should be fun!