My only criticism of Starcraft 2 was how short the single player campaign was, so my least favorite levels were the ones that didn't exist for the Protoss and Zerg campaigns, but should have. My interviewer didn't seem to appreciate that answer.
I start collecting issues and problems to be solved. Make sure that we can agree on a set of objectives. The include people in the a brain storm session. Next evaluate ideas vs. problems to be solved. Next a analyze costs and reruns and stack rank portfolio.