I had the great fortune to come across a copy of Games and Game Leadership by Charles F. Smith (the 1949 13th ed; the first was published in 1933). Though it mostly refers to group games of physical activity for children, many of the principles apply to running table-top role-playing games (and parenting). Professor Smith taught a university course on the topic for many years. Here are some excerpts (in quotes), paraphrases, and notes (in italics) on how they may apply to modern RPG game mastering (dungeon mastering, storytelling, whathaveyou). Some of these do not apply very well, but I include them for interest.
Be Enthusiastic. Enthusiasm is contagious. Enjoy your work. An enthusiastic GM may have an easier time engaging the interests of players, and have a lower chance of burnout.
Develop a Sense of Humor. Be human and share in the fun of the tasks rather than being a dictator. If your players are engaging in a lot of humorous table talk instead of focusing seriously on the game, accept that that's what they're enjoying and roll with it.
Overlook Mistakes. Be sympathetic and understanding. "The person who makes he mistake invariably feels worse for having erred than any one else. If he blunders due to lack of skill, the leader should help him to develop the necessary skill. Every one who participates in athletics appreciates the coach who subtly points out errors in a general way rather than one who constantly finds fault with the individual members of the team." If someone gets a significant rule or mechanic wrong, you can remind the table of the rule while being considerate of the player's feelings.
Anticipate Blunders. Anticpate common blunders and check them without interrupting the game (like the rafting instructors blocking the bad routes on the river). "Individual reprimands are warranted only when the act in question threatens the moral growth of the entire group." Maybe put some bookmarks in your rulebook or photocopy frequently referenced rules or tables to help people play quickly and accurately. Scold people who seem to be bending rules on purpose.
Be Lenient. Do not nag. Let the kids have fun and not play in an exact way (but they still have to follow the rules.) Rules may be less important to follow in an RPG. Charles was mostly writing from the perspective of adults teaching games to kids.
Develop Confidence Through Preparadness. "Confidence is acquired through experience, but even the experienced leader enjoys such confidence only when he is thoroughly prepared to do the particular
work at hand.... He sees ways for improving both the game and his leadership and is able to say the right thing at the right time, in order to create either the desired moral effect or happy morale. ...the way to win respect is to be prepared, even refer to notes if necessary." Be prepared, that's the Boy Scouts' marching song....
Guard Against Overconfidence. You don't know everything. Invite suggestions as to new ways of playing old games or to draw assistants to your confidence in the making or executing of your plans. Don't pretend to be perfect, it just makes you look foolish. I have greatly enjoyed running a huge game with a couple assistants, and I have enjoyed being a player in a game in which the players' input was solicited and used. Not only is humility a great virtue, games are easier to run and more fun for the players when the GM accepts input and help.
Conquer Trying Situations. Maintain poise, striving always at least to appear at ease when vexatious situations arise. "Avoid petty squabbles." Stay calm. This is good advice all the time. Be cool.
Adopt a Positive Attitude. The descriptive text indicates that this means Be Decisive in modern English. Make the decisions instead of deferring authority to someone else. The GM makes the rules calls. The GM's word is law. I'm in favor of a One Appeal rule, but after the appeal the matter is settled. Be assertive without being aggressive. Be clear and firm. Don't let a friend or overbearing player make rules calls for you.
Lead Just Enough. "Lead just enough to set the pattern without crushing the initiative of the players." Children need experience with self-direction under supervision since they are not always supervised. Don't railroad your players.
That's enough for part 1. I've got a few more for part 2, then a follow-up post or two from another section of the book. Good stuff.