Very good advice from all the above. The only thing I can add is to consciously aware of everything that is going on around you, both inside and outside the airplane. In your mind, have a reason for everything that you do, every switch you touch and everything that is said on the radio, or P.A.
Think of "command" as having to sit on a witness stand one year from now and be able to answer very tough questions from some lawyer who has had a year to disect an action or desision that you may have had only a second or two to make.
Use your crew. Don't try to do everything yourself. Delegate the mundane stuff like paperwork and flight log to the f/o. Most of them love to do that.
Be careful what you say on the P.A. It's always best to tell part of the truth, speaking more in generalities than detailed specifics. Most of the people behind you are apprehensive about flying to some degree and a reasonable explanation of a delay or abnormality will usually suffice. And there's always at least one person back there who thinks he knows more than he does, and will be your most vocal critic.
Good luck to you. It's the best job in the world. You'll love it.