Deadspin has found them! And as such, I thought them worthy of review and discussion in this space. Plus, although there are 30 such rules, I gotta think that they missed a few.... so certainly a complete run-down would be good. I'm pretty sure the submissions will be priceless (though maybe let's leave out "Don't get involved in a land war in Asia.").
So as reproduced from a 1986 edition of Baseball Digest, here they are:
1. Never put the tying or go-ahead run on base.
2. Play for the tie at home, go for the victory on the road.
3. Don't hit and run with an 0-2 count.
4. Don't play the infield in early in the game.
5. Never make the first or third out at third.
6. Never steal when you're two or more runs down.
7. Don't steal when you're well ahead.
8. Don't steal third with two outs.
9. Don't bunt for a hit when you need a sacrifice.
10. Never throw behind the runner.
11. Left and right fielders concede everything to center fielder.
12. Never give up a home run on an 0-2 count.
13. Never let the score influence the way you manage.
14. Don't go against the percentages.
15. Take a strike when your club is behind in a ballgame.
16. Leadoff hitter must be a base stealer. Designated hitter must be a power hitter.
17. Never give an intentional walk if first base is occupied.
18. With runners in scoring position and first base open, walk the number eight hitter to get to the pitcher.
19. In rundown situations, always run the runner back toward the base from which he came.
20. If you play for one run, that's all you get.
21. Don't bunt with a power hitter up.
22. Don't take the bat out of your best hitter's hands by sacrificing in front of him.
23. Only use your bullpen stopper in late-inning situations.
24. Don't use your stopper in a tie game—only when you're ahead.
25. Hit behind the runner at first base.
26. If one of your players gets knocked down by a pitch, retaliate.
27. Hit the ball where it's pitched.
28. A manager should remain detached from his players.
29. Never mention a no-hitter while it's in progress.
30. With a right-hander on the mound, don't walk a right-handed hitter to pitch to a left-handed hitter.