Thom Hogan over at bythom.com has written a very helpful essay called "What's Your Goal?" that I commend to your attention. It takes up where my more fundamental essay "Getting Better: The Crucial Sentence" leaves off.
Thom's piece is very well done and I don't mean to criticize it, but there is one tiny flaw in its logic. At one point he counsels that for goals to be useful, they should be ambitious. As an expert in this sort of thing, I happen to know that this is circular reasoning. Ambitiousness is a predicate of goals in the first place. You must have ambition to feel you need goals, much less get to the point where you can write them down. All goals that are clear enough to write down and not be embarrassed about are already ambitious. It's a small point.
Now I'm going to scratch one of my own goals off the list. It was, "Write a clear, concise, and above all practical essay for photographers about setting goals, or find one somebody else wrote that is as good or better than I could write myself." Then I'm going to take a rest. Achieving one's goals is satisfying, but tiring.