If you've been reading so far, you may recall that I'm not a fan of hit points. While I agree that they're an easy way to figure out and track how much damage a character can take, they fail me on two counts:
You can't do one-shot kills - when a foe has more than 1 HD, you usually need multiple hits to bring him down, and
You can't simulate performance degradation - meaning you're just as effective at 1hp as you are at 50hp
Since goofing around with Swords & Wizardry, it occurs to me that hit points are here to stay. I mean, I solved the issue with Chimera, but how do I simulate these things in S&W?
Here's a possible solution, with the added benefit of being able to use S&W stats without modification. In other words, it's a modular option that will work with existing material.
When you take damage, you have a choice:
Soak it up - this option subtracts the damage from your hit point total, pretty much like you do now. The idea here is that hit points represent your mental/physical ability to deal with getting battered, hurt, hit, crushed, nicked, bruised, etc. When your hit points fall to zero, you're "vanquished."
Take a wound - this option ignores hit points, but each wound imposes a cumulative penalty of -1 to your movement rate and all rolls (and I mean ALL rolls—attacks, damage, searching for secret doors, wandering monster checks, etc.). A wound's severity equals the damage inflicted, though severity does not affect the wound's penalty. You get a maximum of 1 wound per hit die; any more than that, and you're "vanquished."
Getting vanquished doesn't mean you automatically die, but it does mean that the victor (i.e, your opponent) decides what happens to you. That might mean you're captured, knocked unconscious, forced to flee, or (sadly) you get the killer blow. But PCs get a saving throw vs. a killer blow (if they succeed, they're unconscious for awhile and wake up with some permanent or temporary injury).
How Does This Help?
There's one more piece to the solution: exploding damage die. If you roll a critical (whatever a critical means in your game), the damage die explodes, meaning that if the roll shows the highest value for that die, you roll again and add the result. You keep doing this as long as you keep rolling the highest for the die. 
This takes care of one-shot kills: rack up enough exploding dice, and you can drop a foe with one hit. Obviously, this is harder to do for opponents with lots of hit points, but it's still possible. Even though you'll still see opponents with crazy-high hit points, I think it's enough that this system allows for the possibility. 
But let's say my character gets hit with enough damage to drop him instantly. I can avoid it by taking a wound instead. This leaves my hit points intact, but now I have to accept a penalty to all my rolls (plus what amounts to a really severe wound that will take awhile to heal).
So here's the deal:
Soak up damage when you have enough hit points or when you want to avoid a performance penalty
Take a wound when you want to avoid a one-shot kill or you're low on hit points
I've been toying with an end-of-adventure XP bonus based on damage taken, based on the logic that enduring physical or mental pain is probably a learning lesson.
In this model, you get 100 XP for every wound taken, but you also get 10XP for every hit point remaining at the end of the session. Clearly, this is incentive for characters to take a wound, which may cross the line into evil GM territory, but I still like the idea.
Healing works normally, except you can apply healing to wounds or hit points. Wounds are healed (and their penalty goes away) when their severity is reduced to zero (e.g., it takes 7 points of curing to heal a severity 7 wound). The big benefit here is that there's no change to the S&W healing guidelines or to curative spells and magic items.
What I like about this system is: (1) characters can dictate their fate a bit more (lose hit points and remain at peak performance, or take a wound to save hit points), (2) it simulates the negative effects of getting your ass kicked, and (3) it works with the existing stats, so you don't really have to do any rewriting or conversion.
Assuming this model has potential, what needs to be tweaked and adjusted?
I'm still working out the details for critical hits in my S&W game, but I think they work like this: Each character has a critical hit range on the attack die, equal to 20 minus his class-based to-hit bonus. Check the revised to-hit chart I posted last week, and you'll see that fighters will crit most often, followed by clerics, thieves, and magic-users. For example, a 4th-level fighter has a to-hit bonus of +2. If a to-hit roll results in 18, 19, or 20, and the attack succeeds, it's a critical hit. There's more to this, of course, which I'll reveal anon.
Fussy-pants that I am, I have a solution for that, as well. More details to come, but for now, suffice to say that when you gain a level, you have the option of "trading in" your hit point roll for some other advantage. The net effect (for PCs, NPCs, and monsters) is a chance of less astronomical hit point totals.