So you think the former
stage manager had everything under control and for all intensive purposes an easier time ha? Possible with experience, but not very likely on the whole.
Never loose your cool. Discipline in private, praise in public and don't forget to say thanks. If you loose focus you are not doing your job be it tunnel
vision - focusing upon a small project and not the overall picture, or in thinking about other things and not the show. That's something to battle and master. Delegate and supervise but don't get overly involved in being the one to actually do things. Again, never show yourself loosing your cool, having a temper or getting distressed. People are looking up to you as their leader. If the leader gets lost, there is not much hope for the rest of the crew to also not get lost.
You need to find your own style of leadership and for each person it's unique. That for the most part with experience, note/record keeping and especially being very organized will be the things necessary.
Leadership, might find a short
book on it in the library, or online. Lots of styles, your unique style probably needs honing. Should not matter if you are an amature around pro's, if you are a leader, they will follow if you know how to lead. The best leaders are also the best followers. Delegate to the followers you trust, and assign tasks to those less trustworthy. Check up on them and have them report back when the task is done. This will most likely take a lot of tact and leadership, plus a good solid memory for the details and verification it's all done. Verifying it's done not in a panic'd did you do this way, or one that shows you don't trust, more one that it's your job to verify such things. Find them around the soda machine, that's a leadership issue.
The person that complains the most such as "I mopped the
stage last time" is a prime candate to be in charge of who does such tasks on a day to day basis in reporting directly to you. One less thing to worry about keeping
track of, and one less person complaining to you. Also once given some authority or responsibility they are partially in your shoes and become an ally on other things. They will either do a really good job at it or fail and realize why it was difficult for you to do the task to their satisfaction. What ever the case, even if they are not of much value, you will have in some way made them failthful to you. Their
power even if temporary was provided by you. Once they accept you as their boss it carrys to other things. That's part of one thing that works, lots of other things and concepts and ways to lead.
Should also be a lot of books on
stage managing around. I would recommend some light reading into that concept. Good ideas would very likely be there in answering all your problems.