In management consulting, we typically take a hypothesis driven approach. This means, even without getting any data or conducting any analysis, you should start developing potential hypotheses based on the given problem statement. In the following weeks of the project as you gather data, research, investigate and analyze, you are essentially proving or disproving your long list of hypotheses to get closer to the the truth.
For this to work effectively, it is important to be very objective. Don't be attached to 'your' hypothesis; the moment there is a fact based evidence or an analysis that disproves your hypothesis, immediately switch over and accept the better hypothesis and move on. Keep your ego in check as it is less about who's idea it was but more about how as a team we are able to come closer to the truth.