I don't if this helps you, but when you think about tactics of monster, try to think as the monster. Read the description of them and and their type (undead, animal, demon, ...) to get a rough impression of what they are. Then take a look at their stats, mainly intelligence. Are they dumb? Then they don't think much and directly attack. If they are mindless ,they always fight to death. If not, they may retreat. If they are moderately clever they try to use the best option available for them, like using the attack with the best bonus and/or damage, first attacking from range then mabe closing in, if they are good a melee. Clever monsters (like 10+) will also consider the abilities of their allies and match their tactics, like trying to flank the enemy, or some of them keep the fighter occupied while others circle around him to get the wizard. Maybe this provides you with a general idea an guideline.