I am in TOTAL agreement with the others about teaching your horse to stand still while you mount. We are doing just that with our 3 yr old gelding. For us, it is VITAL that he learns this, because in the future he'll be at some of the largest National CW events (as our hobby winds down.) Things get very hairy and your horse can get very upset by all of the action. Here is our training, which, BTW, we only do only on weekends this time of year. I do NOT have an indoor arena in my back yard, but if my ship ever comes in, I will.

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We lead "Sweet Cup'n'Cakes" into our small arena (55 ft x 65 ft)
We walk him over to our mounting block, and the person NOT riding holds him there.
IF he turns outward on the forehand, we push him back into position (had to do this 4 x yesterday)
Rider plays with the saddle, like hanging on it to see if it's tight
Rider mounts
We count a full 5 minutes before he is asked to move out.
IF he steps forward, we halt, and start the clock again.
I was SO pleased with him yesterday, because my DD was riding our mare, and she left the gate to our small arena open. I worked on both Left Rein and Right Rein (after our halting/mounting practice) and he didn't even ask to leave once! **hugs to my good pony**
I used to train my horses with lessons and lots of different riders. Their manners were perfect. All of my original lesson horses have now passed on, and I don't have the luxery of working them 15 hours a week. So, we work every good weather day we can. It'll still get 'er done!!!