Many of the heroes and villains of Middle-Earth have had to make important decisions, and even their smaller decisions can have huge repurcussions. What if Denethor had sent Faramir north to Imladris instead of Boromir? What if Gandalf had decided to take the Ring when Frodo offered it? What if Saruman had chosen not to side with Sauron?
So, how would different decisions have affected the outcome?