When I worked as a golf professional, one of the best ways that I discovered to diagnose a player's swing problem was this: make them hit balls using one-armed swings. Here's what I did and how you can use the method to help your shot outcomes.
After warming up on the driving range, hit about 10 shots regularly with an 8 iron to get a feel for how you are swinging that day. Then, take your non-dominant hand off of the club and put it in your pocket. Take a few practice swings using only your dominant hand. Make full swings at about half speed being sure to maintain proper form. Now hit 5 shots using only the one arm and note the results. Now repeat with the opposite arm only. Your drill is over at this point.
Why this works: The body is a set of pully mechanisms. In most cases, a player's poor shot outcomes can be traced to one side of the body or the other. The pully system simply is not working congruently. If one side of the body is working properly and the other side is not, you will see the results immediately. When one side has a dysfunction, it can't perform the necessary functions to carry out the intended shot pattern.
More than likely one side will yield better results than the other. You should be able to isolate the major swing problems to the problematic side of your body, and this side will be the focus of your practice. If you practice with the problematic side with little or no results, see a golf professional to work with your swing mechanics and/or your chiropractor to assess biomechanics. This drill has been a huge success in helping players overcome shot inconsistency. Let me know how it works for you!