Mostly, OSR combat is pretty abstract, and that's perfectly fine, but every now and again we want a bit more detail or drama. So I introduce "Ivan's super simple hit location table":
1 Left Leg
2 Right Leg
3 Left Arm
4 Right Arm
No special rules or particularly for hitting a certain location. Just something quick if you really want to know where something hit randomly.
It's kept simple to make it easy to remember. Of course it's more likely to land hits in the extremities, but that may be reasonably realistic for a melee in any event.
As an alternative, for games using 1D6 for damage, the damage roll could also be read as the location. Hence, hits doing 5-6 damage are always vitals hits (whether they inflicted damage or bounced off the armour).
On a related note, if you want to play up the abstract nature of hit points, the key is how you describe combat. Try this: Any hit inflicting in the lower half of the damage range (1-3 on a D6) is a "threat". You were knocked about, the blow glanced off the helmet, you parried but it sent you staggering and so forth.
Any hit in the upper half (4-6 on a D6) are actual injuries, ranging from life threatening wounds (on a level 1 character) to gashes and broken ribs (on a higher level character).
For bonus points, try it without the players knowing their hit point totals.
Don't be afraid to leave comments, particularly if you've done experiments with how to treat hit points in your campaigns.