Here's a horse training tip that will teach you how to naturally cure a buddy sour horse. This seems to be a common problem among horses and this horse training exercise will show you how to nip it in the bud.
Horse Training Tips: How to Train for Barrel Racing, with Video
Barrel Racing: Training the Wright Way (Masters)
There are so many tricks you can teach your horse. There are all the usual ones like kiss, hug, bow etc, but also have a think about teaching your horse some USEFUL tricks. These can make life a lot easier (and safer) around your horse.