Damage oh the humanity!
In the classic AD&D approach you are a blob of goo. Able to function no matter where or how heavy you are hit. That's great for a cliche "hero" or Energizer Bunny. However, we place more emphasis on role playing. Both the good and tough aspects of giving some realism to a character.
A humanoid body is divided into 12 areas (boxes). Each box consists of a grid of spaces equal to the characters Constitution score (rounded up). Damage is marked like a bowling score. Bruise damage is a / and regular damage is an X. Additional boxes can be added to specific body areas by employing the advantages of armor.
During the course of combat, if a hit is scored, the attacking character simple rolls a d12 to determine which area of his/her opponents body is hit. If you don't want to take your chances with the dice you can roll called shots to hit a specific area at a cost of -3 to hit.
What use is this? Well if Grog is constantly getting cracked in the melon he may change his fighting approach or fork over some coin for a helmet! No big deal right? Not if you want to add depth to each adventure. If a character has a heavily damaged knee it will remain recorded on the leg area until enough healing, or time is used to repair that area. This should keep the players from ignoring or forgetting that really big hit he/she took last fight or last adventure. That's right folks, an actual record of damage from the last outing.
This box system also adds strategy to a fighting style. Grog can work on an opponents weapon arm until the enemy cannot use that limb by employing called shots. The opponent must either retreat or fight off handed while loosing blood. Now instead of always being in a fight to the death the player must consider his/her alignment, religious convictions, etc. Would he cut the enemy down ruthlessly or leave him to fend for himself.
Here is a sample of a humanoid box area set with a constitution score of 16 and no armor. Note the order of body areas 1 - 12. It is helpful to keep the area definitions consistent.
To promote consistent play, use the damage chart for NPC's as well. If you like to bring interesting NPC's back in other adventures, now you have a record on that character. Maybe the NPC shows up with a limp, or patch over one eye as a result of their last meeting with the party. The players may have just given you a good revenge plot for next time.
I know it looks like a high level character should be able to max out a box area in one shot. Well maybe they can. But the characters should play with better fighting styles, or choose their fights more wisely. "Well gee-wiz Grog, maybe you shouldn't taunt any more giants!"