In core rules, the only way for a character’s learned skills to change is for the character to gain a level and spend skill points. It is not possible for an unused skill to lose ranks, nor is is possible for the character to learn a new skill, regardless of what he is doing, without gaining a class level.
This article describes a way to allow a character to change, without requiring him to gain a class level.
This article describes how I develop information for my campaign. The focus is on events and entities (characters and things), but it does have more far-reaching effects when applied.
The techniques described here are based on an article written by Dariel Quiogue, in turn a synopsis of research and theory by an historian named Arnold Toynbee. It also tieds in ideas form the Dungeoncraft column, originally written by Ray Winninger in Dragon Magazine.