What's the Problem?
Any time I'm faced with a task, I find it useful to look at it in terms of problems, processes, and solutions. This applies to all aspects of life, but since this is a marketing blog, presume we're talking specifically about marketing.
Although looking at a situation might give you an initial gut feeling that turns out to be right, challenging your assumptions and working through the process to ensure you have identified the problem correctly is still an important exercise.
This doesn't have to be a long, drawn-out process if the problem and answer are obvious.
In fact, it is for that reason we're able to function every day without drawing all our thoughts on paper to ensure our logic is flawless before proceeding.
We do it on the fly, because it is in our capacity to do so, and we're right enough times in our day to keep the engine of our economy turning.
If logic, however, is not your strong suit, or you cannot conclude your assumptions with a reasonable degree of certainty, first, endeavor to improve.
Second, set up your systems so that you can fail, learn, and improve quickly.
This not only helps improve your ability to reason, but it also improves your instincts, which may help you identify your problems more accurately on your first try. - Cam Beck
P.S. Seth has a nice post about "Layering" that speaks to the ideal of a quick-learning system.