Pathfinder 2e General Discussion

Usually, attacking 3 times is a pretty good option for monsters, since they have such inflated attack bonuses. It is really good to model good tactics for your players if you remember to, though. (I usually forget to do this.)

For more intelligent monsters, have them step back out of melee range with their 3rd action, or open with a Grab, Trip, or Demoralize. Those are actions any monster with the skill can take.

Generally if a monster has a unique action, you should use it as soon as applicable (even if it's not technically the best action to take). Monsters have limited screen time, so make sure to showcase the unique things they can do!

Monsters can use skills too, so look at what skills they have and what basic/trained actions they have access to. Disarm is a joke until an enemy disarma the fighter and then attacks their sword, destroying it (since it's an unattended object). Also, your players might hate you if you do that.

Move around, if you are going to make a 3rd strike it's probably better to move away unless the player has an Attack of Opportunity or similar, and even then you can just step away.

Use terrain more. The mosters are usually on the defensive in my games, so they might have traps, advantageous terrain, etc. If the enemies are shooting from a balcony then they are not in melee range, and probably can Take Cover each round. If the usually melee PCs made the mistake of not carrying a ranged weapon they'll need to either find the stair up or climb which is not ideal.

Use (magical/alchemical) items! There's quite a long list of them and I feel they are underused in the game, my players at least have this "I might need it later" mentality, specially (but not only!) towards consumables. I personally blame Final Fantasy for that, oh well.

Basically any advice that works for the PCs is going to work for the enemies tactics-wise.

I don't know of any resources, but what I do is using skill actions. Athletics, Deception and Intimidation are what you'll be mainly looking for because Athletics has a lot of fun stuff on it, Intimidation is Demoralize and Deception is Feint.

But never attack thrice, moving away is better even for meele and unintelligent monsters. If you look into animal fights videos you'll see that, unless they're grappling, they always do the back down-charge!!-back down-charge!! cycle as well. Even lions hunting larger prey do that.

He get some fun in encounter by using Demoralize and combat maneuver. Players always fear when I roll for a grapple or a shove to make them flat-footed between two monster.