After each room in which some challenge was overcome (at least one GM instituted resolution was made in the room), a character may make a roll to see if his character learned anything from his experiences there. Success means that the plus one bonus is acquired. Failure means that the skill, familiarity, or item rating goes down by one (which can take the rating negative). These can take one of a few forms:
A character may attempt to learn better how to use any item that they used in the room, thereby increasing their Item Familiarity rating for the item in question by one. Gear familiarity starts at zero for every item acquired. The player rolls using the skill used to use the item as the bonus |fight, for weapons, for instance|, and the associated attribute, vs the familiarity with the item being targeted.
A character may improve a skill (or skill specialty) that was used in the room, attempting to increase their bonus by one. They roll using only the skill's related attribute for bonus, vs the rating that is being targeted.
A skill that is not known cannot be improved using the above rule. But if the party retreats to a safe area, where they have time, they may elect to have one member instruct another in how to use a skill.
If the party retreats to a safe area, where they have time, space, and the appropriate gear to work, the character may make a single attempt to improve a single item rating by a bonus of one by making a crafting attempt. An item that has any of it's ratings brought below zero is broken, and is discarded as worthless, the character losing all associated bonuses for the item.
The bonus rating for the opposition is equal to 5 times the rating that's being targeted. So to increase a sword's damage rating from 5 to 6, for instance, would mean that the opposition roll would get a bonus of 30 to the roll. If the player's total is equal or greater than the opposition roll, then the item is improved as planned. If the roll is failed, no improvement occurs, and in fact the item loses one in the rating in question for each full five by which the roll was missed.
Astute players will note that it is often much easier to give an item a specialty rating than it is to increase an already high primary rating, though these of course have less broad usefulness. The classic example is adding +1 Sharpness to said sword, which is a specialty of the damage bonus that only applies to targets not wearing metal armor.