(1) Check with the rules first, they may have something definitive to say on the matter. Some do, others don't.
(2) Forget what the book says (unless the game has an extremely detailed mechanic that links hits to physical injuries) and decide what works best for your own game. Practice makes perfect.
(3) Understand that if you can somehow circumvent Chuck Norris' considerable martial defenses, you can kill him with a paring knife if you stick it in the right spot. And keep in mind that in most games, such weapons deal MINIMAL damage...
Now, assuming hits represent PHYSICAL TOUGHNESS ALONE, an 18 HP fighter is either NEVER HIT in the femoral artery or is IMPERVIOUS to such injury against all evidence to the contrary.
|Ouch! The tremendous ability of|
characters to survive injury can't possibly
be ALL physical, now can it?
Of course, the final, killing blow COULD be to the femoral artery, but it takes a LONG time to get there - and probably not because the victim has accumulated too many nicks and scratches...
On the other hand, when we recognize that hit points represent a COMBINATION OF BOTH SKILL AND TOUGHNESS, this makes sense, and gives you some idea of where WE stand.
So, which hits are deftly avoided strikes and which are authentic physical blows? We use the following:
(1) Narrate combat and pull creative descriptions of hits and skillfully avoided misses out of your keister!
(2) Let players describe their attacks and make on-the-spot judgments about whether or not a "hit" is a true physical strike or cleverly dodged, etc. This gets players involved and lets them assist you. If they mention raising up their shield and the enemy hits them anyway, say the blow glanced off. Over time, a fun narrative dynamic takes over, and the hard-and-fast rules governing combat will keep things objective...
(3) Injury taken to the bottom ONE-THIRD of total hits is largely physical, and the FINAL KILLING BLOW IS ALWAYS SO!
Hit points are survival for any cherished character, and the relative strength of enemies is equally so, as physically tough foes are harder to kill and more likely to turn the tables. That said, objectivity is important, and players are more likely to accept the death of Bjork the Bold when everyone understands the rules and accepts that they died "fair and square". At the same time, combat can be heroic and exciting without invoking ANY rules.
Understanding hit points as a measure of SURVIVAL ABILITY that sometimes involves skill and luck helps. So does narrating battles and letting players contribute to the fun through their in-game descriptions. And don't worry. By defaulting to the rules for hit resolution, things won't devolve into questionable territory!