Use general hit points for most foes?
That way the only thing choose location does is change how many AP the foe have. IE. It makes choosing the head actually worse than other locations.
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And apart from that I really don't get the fuss about choose location: Head, (as long as it isn't coupled with stun location which can be fight-ending).
The difference between hitting somebody in the head and in the chest is 2 hit points. And I mean the result of reducing the location by that amount of damage is identical.
An arm even has 1 hit point less than the head, meaning only 5 points of damage is needed to cause a wound, if you impale instead the higher average damage will mean you more often than not will cause you opponent to lose 1d3 CA, and lose the use of his arm. And I mean, who's gonna keep figthing without one arm when he's offered a choice?
I plainly suggest to only use choose location if there is a vast difference of AP, if the opponent has cover (in which case it's essential), or if the opponent is already severely damaged in one location. (since reducing a location to a Major wound is pretty much the same as killing him).
Just have your own mooks use the more useful CMs (your players will soon catch on), here's the rundown of when they are useful:
Bash Opponent - The stable of the longer reach man, forcing your opponent back means he'll have to close again, giving you options to either keep him at a distance where he can't attack you, or giving you options to strike him again and keep bashing him away. Bash is better than changing range when you want your opponent to further his distance from you, since it has the added possibility of him tripping over something or someone.
Change Range - If the opponent is too big to be bashed, you are probably screwed at long ranges, due to their usually high reach, changing to close ranges makes the opponent unable to defend themselves, but beware, high SIZ means high damage, so get ready to take a beating. I prefer changing to close range when I have superior armour (usually through shapechanging or a shield spell, but I guess plate would work as well).
Disarm - Disarming an opponent requires him to pick up his weapon from the ground, and can be made more easy with a two-handed weapon. If you opponent has no weapon, he's got a hard time fighting and this forces him to waste a few CAs to get his weapon back. CAs are the most important thing in combat so this is a supergood use. It's best used against enemies with low skill and only one weapon, or when you make a good roll to hit. Note that this ability can be used defensively, which is a huge boon, often turning an otherwise useless shield CA (if playing with the off-hand action optional rule) into an advantage you get in your opponents turn. Also note that the take weapon CM is strictly superior, but dangerous, since it requires you to be unarmed, and thus you can risk taking damage if you opponent succeeds his attack roll, a good unarmed skill (120+) or your opponent having a small weapon would still make this a viable tactic though.
Trip Opponent - Tripping does a bunch of things, first, it forces the opponent to waste time on getting back up, secondly, it allows you to change the distance. Tripping is opposed by evade, which means big and clumsy opponents will suffer to it often. Being tripped does not only give you an all your allies +20% to attack the target, it also gives the target -20% on all checks to defend, meaning it is the most effective "debuff" out there.
Grip - Unarmed maneuver that is offensive, yet does the same thing as pin weapon, but requires your opponent to use unarmed skill to get his weapon back. If you have a good unarmed skill this is golden.
Sunder - Essential for taking big mooks, sunder some armour, and everybody follows up with choosing that location, piling damage on the same location this way is probably the best use of the choose location CM, and the simplest way to taking down big baddies like dragons or their ilk.
Bleed - Bleed is good if you have the luxury of time on your side, if your enemies are many but can't all engage you at the same time, or if he's normally heavy armoured, bleed can make him go down to fatigue as you dance around and away from him. Using bleed properly requires you to have good move an evade so you don't need to face enemies that are bleeding and can get away from them.
Impale - Since you lose your weapon. Impale is mostly for ranged weapons that make good use of it with their big size and no real downside on it. Using it in close combat is very dangerous, since it costs you multiple CAs to get your weapon back. This should rarely be attempted without a back-up weapon and not if there is still an the same amount of combatants on both sides.
Stun Location: Stun location is a great way to take a combatant out of the combat early, if you hit anything but an arm, the opposition is basically out on a failed resilience roll. If you hit an arm, his usefulness is reduced.
The critical effects give themselves away, when your opponent has better armour than your average damage, penetrate armour is the thing you want, when he has low armour, maximise damage is the thing you need.