As I'm sure you can imagine, opinions on Step 2 run the gamut. With that being said I've found the best approach here is also the most simple; stick to what the big book tells us and look at our own experience and that of others.
Let's start with what the book tells us. Step 2 begins on page 44 (We Agnostics) by saying "If, when you honestly want to, you find you cannot quit entirely, or if when drinking, you have little control over the amount you take, you are probably alcoholic. If that be the case, you may be suffering from an illness which only a spiritual experience will conquer." In Step 1 we learned that the real problem of the alcoholic centers in his mind rather than in his body, that we are literally insane when it comes to the ability to control the decision to take that first drink or not. Only with a clear understanding of the problem can we find a solution.
"Lack of power, that was our dilemma. We had to find a power by which we could live, and it had to be a Power greater than ourselves. Obviously. But where and how were we to find this Power? Well, that's exactly what this book is about." Page 45 breaks it down pretty simply for us, we need God. When I'm taking someone through the steps I just ask them a few simple questions around Step 2. Do you believe that I drank the way you drink? Do you believe there is something beyond my own power keeping me from drinking? Are you willing to believe in a power greater than yourself? If the answer to these three questions is "yes" then we can move forward. It's that simple.