Action Economy
Source GM Core pg. 127
Understanding a creature's action economy is key to making it work in play. Remember how short the lifespan of a typical combat creature is. Including a bunch of combat abilities might mean you spend time building actions the creature will never have time to use. Narrow your selections down to the smallest and most compelling set that makes sense. Also keep in mind that special actions will compete for time with any combat spells you give the creature.
Reactions can help, giving the creature a way to act when it's not its turn. See Reactive Abilities for advice on designing these tricky abilities.
Because of PC capabilities at higher levels, creatures at those levels should get more abilities that improve their action economy. For instance, creatures that grapple should have Improved Grab instead of Grab, Speeds should be higher, and many abilities that would've cost an action at a lower level should be free actions.
Reactions can help, giving the creature a way to act when it's not its turn. See Reactive Abilities for advice on designing these tricky abilities.
Because of PC capabilities at higher levels, creatures at those levels should get more abilities that improve their action economy. For instance, creatures that grapple should have Improved Grab instead of Grab, Speeds should be higher, and many abilities that would've cost an action at a lower level should be free actions.