I bought a mirror just for that.
Next to video tape, a mirror is one of the best training aids available to the serious shootist.
I seem to recall one of the old timers like Bill Jordan pointing that out.
I use mine to see what I am doing wrong.
For example, by hitching my holster in a different position on my hip, it helped me to avoid grabbing shirt tail on a speed draw or "presentation" as the cooper troopers call it.
In a pinch it can also be used to check on your form and sight picture. With your back to the mirror, draw your arm spin around, and get a flash picture then stop before you pull the trigger.
Are your sites lined up properly?
Because of this mirror training, my fine motor skills are a lot finer than they were before I began using the mirror as a training aid.