Questions about my skill system are pretty popular. I've covered some previous questions here.
This skill system is one of the best I've ever used, and I've used a lot.
It has basically solved all my skill system problems. Like Fudge, it allows you to determine what skills are right for your campaign, but is more dynamic then bell curve resolution. It can have the mechanical usefulness of 3.x style skills, but isn't tied into level and bypasses the large variability inherent in the d20. It allows anyone to attempt any skill yet still provides bonuses for the people who possess the skill. Odds of success and improvement are easy to calculate. And, as this question notes, the fact that the skill has three distinct levels, allows it to have more powerful or useful effects as you become more skilled.
Let's look at the healing skill:
Healing: A successful use of this skill will heal the user of damage after battle. Those unskilled heal 1 point. At skilled this heals 1d6+1 points of damage, at expert it heals 1d8+3 points of damage and at master it heals 2d10+5 points of damage. This may only be used once per wounded person per fight. It takes one full turn to use per person.How did I come up with the amount of healing at each skill level?
Well, this skill in particular comes from Numenhalla, my mega-dungeon campaign. Numenhalla is wonderful because a mega-dungeon has a very specific limitation in both time and space. Therefore each skill can be very specific and mechanically tweaked for this environment. In my more recent Deathless Gods campaign, the healing skill didn't heal any damage. It instead dealt with critical effects.
Why did I add the ability to heal hit points? Because of the way classes are structured in Numenhalla, it is very unlikely that there will be someone along who can cure light wounds. Without healing from spells, there should be another mechanic available to restore hit points.
How did I arrive at these levels?
First is the cost and limitations, the attempt takes 1 turn after a battle. It has to be used immediately after. This cost (time, torches, wandering monsters) makes the skill an interesting choice in some situations.
Untrained people should have a shot at stopping bleeding and rousing people after battle. 1 point will bring somebody above 0 hit points and stop bleeding.
Being skilled heals from 2-7 points of damage, effectively removing 1 hit taken in combat.
The expert level provides a much better bonus, healing 4-11 points. Unlike the first level, the worst you can heal is 4, and the average will be 9. This is a pretty substantial number of hits in B/X, likely between 20%-50% of the fighters hit points till sixth level. This means that an expert healer can restore a goodly amount of hit points.
It is not noted above, but the default difficulty of the roll is 5, this allows an untrained character to succeed 33% of the time, and a skilled character to succeed a full one-half of the time. This is astoundingly close to the first aid DC 15 in pathfinder. Someone with 0 ranks will succeed 25% of the time, and a first level character with 3 points in the skill, plus 1 or 2 for the stat will succeed 45-55% of the time.
These values would have to be modified if they were to be applied to a system that utilizes higher hit point totals. In B/X fighters only receive a d8 per level, and are unlikely to have a constitution modifier of higher than 1.