TMAT Rules of Thumb

General Maxims:

1. Archers are swordsmen.
2. If you're a hero model, don't ever whirl with a two-handed flail. Don't... just don't. However, if you're a warrior, you're engaged with 2+ enemy models, and you have a spear supporter, you should definitely Whirl with a two-handed flail.
3. Shielding will never win a Lords of Battle game.
4. Siege engines don't like maelstrom fights, but war beasts and chariots LOVE maelstrom fights.
5. Spells that improve from a +1 bonus (or a -1 debuff) to a +D3 bonus (or a -D3 debuff) will get you nothing extra some of the time - but it will make your opponent try to stop the spell more (if the spell can be resisted).
6. When casting a spell on an enemy model, shoot for at least a 70% chance of success. 
7. When casting a spell on a friendly model, shoot for at least a 50% chance of success.

Rythbryt's Rules (originally presented in his series on Heroic Strike):

1. In an even duel, both sides have an even chance of winning.
2. Having higher fight value (of any value) than our opponent helps us win the fight, but only if we have a drawn combat.
3. Adding more dice (on its own) is more likely to help us win fights than improved fight value (on its own).
4. [Whirl] reduces our odds of winning the fight, unless we already have a lower fight value than our opponent.
5. Feinting reduces our odds of winning the fight, unless we already have a lower fight value than our opponent.
6. The -1 duel roll penalty from two-handed weapons dramatically reduces our chances of winning the fight, regardless of our fight value.
7. Shield when we need to win selective, short-term duels if we match-or-exceed our opponent's dice count, and/or we match-or-exceed our opponent's fight value.
8. Take banners. Take banners always. (No, duh.)
9. Charging cavalry, with higher Fight, will win (and wound) a lot of fights.

Tiberius's "Guidelines" for Might Points (originally presented in his post on the Top 5 Ways to Waste Might Points and 5 MORE Ways to Waste Might Points:

1. Boost rolls that will guarantee a result (like boosting a To Wound roll vs. a To Hit roll).
2. Call heroic actions that will get you something (not just give you the opportunity to do something).
3. Channel spells that make a difference.
4. Call Heroic Strike when it actually matters.
5. It's okay to move second (though this point is hotly debated by many players, especially Tiberius).
6. If you can't a spell successfully, don't boost it to make resisting it harder.
7. Channelling a spell when you only have one Might point left is a huge risk.
8. Boosting a To Wound roll to get the first wound on a model with 2+ Wounds a 2+ Fate is probably not going to result in doing any actual damage.
9. Heroic Shoots are only worth calling if you have a hero who is about to be shot to death and can shoot before dying.
10. Boosting a dueling roll to force your opponent to spend Might (called "escalating") might not be better than boosting a Fate roll.

Tiberius's "Guidelines" for List Building (originally presented in his Bare Necessities series):

1. As much as possible, you want at least 4 fast models (10" or more of base movement) in your army. When this is not possible, include ways to boost the speed of your army (a priori is Heroic March, though War Drums and Heroic Combats can be used as well).
2. Always bring 1+ banners. While actual banners are best, heroes who are treated as banners (or objects that give banner-like rules) are fine too. If you don't have an actual banner, you need to prioritize killing your opponent's banners.
3. It's best to have at least 30 models in your army when playing above 500 points. Taking fewer models should be done only if you're getting something good for the trade.
4. Incorporate several ways of dealing with enemy heroes. This can be done by feeding them models slowly, avoiding them, fighting them asymmetrically (shooting them to death, using magical powers, racing in with powerful combat heroes if they have weak combat profiles), or taking them head-on with a hero who can beat them where they are strong.
5. You can increase the effectiveness and survivability of your heroes by getting extra wargear, bringing augmenting magical powers, and specialized heroic actions. The greatest way you can help your heroes, however, is understanding your match-ups for the round.