The first of these is:
Keep your word. Don't make promises you can't keep.The effect of someone who keeps promises can be seen in the taking of Sardis by Cyrus. Cyrus promised his troops that the first man to scale the walls would receive a reward and this prompted Hyroedes the Mardian to scale the cliffs and invade the city (Herodotus, Histories I.84-86).
Would someone who did not keep his word inspire someone else to make that risky climb?
The other side of this issue can be seen in the behavior of Gaius, otherwise known as Caligula. He seduced Ennia Naeva, who was married to the commander of the guard, and promised to marry her if he became Emperor, but as Suetonius relates (in the translation of Robert Graves):
It would be hard to say whether the way he got married, the way he dissolved his marriages, or the way he behaved as a husband was the most disgraceful. (Suetonius, Caligula, 25).Caligula's word was not worth much, and although he rose to power on a wave of good will inherited from his noble father, he squandered all the good will away.