Very often, you cannot tell what you are doing right or wrong on your own. Whether it be on the course or the range. Practice is extremely important, but you need a baseline to work from with a goal in mind. I recommend everyone get at least one professional lesson with photo and video recordings of your existing swing. From here you can now feel what you have seen, and adjust / improve from there.

If a pro is not in the cards, then just a friend with a cell phone camera and a decent knowledge of the game will make an improvement...albeit not very significant IMHO