Like a lot of things in 2nd-Ed. Chill, the Skills system is basically left to the troupe's imagination. According to the current system, characters simply need expend the appropriate amount of CIP to learn or improve as many, and whichever, Skills and Disciplines as they can afford and are allowed to have. No thought is given as to whether or not they used the Skill or Discipline during the adventure - or the campaign, in fact - nor how they learn new ones.
The Skills System Expansion (for both learning and improving Skills and Disciplines) applies primarily to campaigns employing the Narrow Skills System, but it also works for Broad Skills. Note that the Vincent Campaign Setting employs both Narrow and Broad Skills (Comp., p. 31).
To improve a Skill or Discipline, the ability must be employed or trained for; the only Skills and Disciplines that can be improved between sessions are those which the character actually used the previous session or spends time developing between sessions. An adventure can span several sessions and a campaign can span several adventures; a session is a single play block. It doesn't matter if the character successfully employed the skill or failed; he learned something just by trying, even if the only thing he learned was what not to do next time! If an ability was Tested, it can be improved without need for further training. If training is needed, an Information Source must be at-hand.
A more common sense approach is needed for learning new Skills (as in, skills the PC does not have). If everyone has some measure of skill in the ability (such as Driving or Sensing the Unknown - "Commons" - skills with a listed Unskilled calculus), then the above rule applies, but the character can also "pick it up" (that is, purchase a Level in the Skill [S, T, M]) at any time. In other words, characters are free to allow "Common" skills to accrue vested CIP and possibly advance naturally, or purchase a Level outright once it has been Tested (whether or not the Test succeeds). A Level can be acquired in any skill with vested CIP. Once a Level is acquired in a skill, it must be employed to be improved. Generally speaking, an Information Source is not needed to learn or improve a Common Skill - check with your CM.
Some Skills should be similarly easy to acquire even though they are not "Commons" - such as Bicycle, Charm, Fishing, etc. Other Skills are more difficult, demanding a certain measure of study and/or mentoring - for instance, one cannot learn Semaphore or Surgery through trial and error! Such skills are so difficult to learn and master that they require special consideration. Martial Arts, for example, costs twice the CIP of any other Skill to learn and improve (Chill, p. 15). But this is the only case where it is built-in to the system; there are other highly-specialized Skills which are not handled by the system as it now stands - and Disciplines are another matter entirely.
When it comes to Skills bought as part of a package or at character creation, the character is assumed to have already gone through the necessary steps to learn them. This may have included some type of formal training (schooling), mentoring, or research, usually at some cost to time and money. Regardless, these requirements have already been met, and the skills can be improved without an Information Source.
Similarly, Art Disciplines (and possibly any Spells) bought at creation are assumed to have been learned previously. In general, the character can be assumed to have been born with these "gifts," if you prefer. Perhaps he had a close relative, friend, or teacher who helped him recognize his ability(s) and even instructed him in how to employ them, or maybe some important experience helped shape what he does and what he knows about what he can do. Still, this happened prior to game-play and the player is free to dictate how his character came to possess the level of mastery he has in these abilities.
Once play begins though, particular consideration has to be taken as to how the character learns new abilities. He can certainly improve those he already has by using them during the session, but how does he learn new ones?
First of all, he must find a Source of knowledge. This source may be a professional willing to mentor him, a teacher, a class or course in the subject, or some printed matter on the subject. The character trying to acquire the new Skill or Discipline must then expend the necessary CIP, then make a successful General PCN check. Failure results in a loss of the CIP without acquiring the new ability (this simulates the loss of time and money), but he can try again.
Improvement in the new ability then proceeds as normal. But the important thing is that, with an Information Source, the character does not have to use the Skill/Discipline during the adventure in order to advance it between sessions. For instance, he need not use Surgery this session to improve it; if he has a copy of Grey's Anatomy, he can still improve his Surgery skill between adventures.
If the CM questions whether or not the character would have sufficient time to devote to this extracurricular study or the self-discipline to see it through, he may require a General WPR check. Failure simply means the character did not have enough time to study the source(s) to advance; he does not lose any CIP he planned to spend. The CM may allow this CIP to be spent elsewhere or consider it "vested" in the skill; they remain attached to the skill to be improved until a successful WPR check is made [see sidebar].
Vested CIP are awarded to Skills and Disciplines whenever they are successfully employed (1) or the CM grants them. The CM may grant any number of Vested CIP to a Skill, Discipline, or Attribute at any time, for any reason. Vested CIP cannot be moved to, or spent on, any other Skill, Discipline, Attribute, or area of advancement; they must be spent on improving the characteristic to which they were assigned.
Abilities can be improved "naturally" through Vested CIP alone. In these cases, the player spends none of the character's general CIP on advancing the characteristic; he just waits until it accrues enough Vested CIP to advance "on its own."