Metagame Combat Limitations (DnD Other)
From D&D Wiki
 Metagame Combat Limitations
A few general rules which should be followed, with exceptions.
1. If an character, regardless of intelligence is engaged in combat it will continue to only fight the original combatant unless a more prominent threat is determined through an assault against the character.
2. When in a battle lull, or previous to an encounter, a creature will never pick an unconscious victim over a conscious threat unless the character is unaware of the threat or a predetermined objective has been set
3. When in a battle lull, or previous to an encounter, an intelligent creature will always select the weaker of a group as the target, unless circumstances mentioned in number two arise
4. Unless of high intelligence or evil alignment, a character or NPC will always attack the enemy who last attacked a comrade, so long as the onlooker is currently not in a battle situation or victim to earlier bias.
These are of course, arguable, so suggestions are welcomed.