What I tell all my Command upgrade students is that the command upgrade is all about people/aircraft management not aircraft handling. A good manager of people/aircraft with average handling skills is always a better aircraft captain than the "Ace of the Base" with poor people/aircraft management skills. A Captain is not just a really good first officer!
Think of possible problems (eg engine failure, sick passenger, uncontained fire, possible ditching etc) and play in your mind how you would manage the problem, not the aircraft handling side but the mangement side. Think about good Captains that you flew with in the past and ask yourself what made them good Captains, and what lessons could I take from them.
Know your Airlines' SOP's, your aircraft FCOM1 backwards, forwards and every way round.
Above all be prepaired to make a decision, and then stick with your decision. When required you can change your decision in light of new information, but make a decision!
All the best.
C100driver
