The best thing my wife did for me, I might add without me knowing it, she took photos of me while I was shooting, it showed me the inconsistency on some shots, it was a big help.
Now some on here have said had someone take a video, I think that would be better, although the photos in my case did reveal what I need to do to have better form.
Consistency in your form is the best thing you can do for yourself.
Master of the longbow I , Rick Welsch instructional hunting shooting DVD, is another great one. Rick Welsch is more back to the fundamentals and the basics, and that's where it's all at, doing the same thing over and over consistently
Carl