I don't know how many of you follow the MGL on Baseball blog, but I recommend it. He posted his 14 Commandments for Managers for in-game strategy. He offers them with this comment:
Here are the first two.
Note: These are rules of thumb which apply 90-99% of the time (or so). Some of them have a few or even many exceptions and nuances to consider. I do believe, however, that if every manager followed these religiously, even without employing any exceptions or considering any of the nuances, that he would be much better off than the status quo. There are also many other suggestions, commandments, and considerations that I would use, that are not included in this list.
Here are the first two.
1) Though shalt never use individual batter/pitcher matchups, recent batter or pitcher stats, or even seasonal batter or pitcher stats. Ever. The only thing that this organization uses are projections based on long-term performance. You will use those constantly.
2) Thou shalt never, ever use batting average again. wOBA is your new BA. Learn how to construct it and learn what it means.