In many RPGs (or at least the ones I've heard of) the alignment system tends to have two definitions of a true-neutral character. Generally, they are something to the effect of what follows.
Definition 1.) Someone who does whatever seems to be the best idea at the time. They do not have an urge to do what is 'good' or 'lawful,' but neither do they go out of their way to avoid doing things in that manner. The same is true of 'evil' and 'chaotic' actions, with the major difference on how they view the other alignments being that lawful and/or good societies tend to be more appealing to live in to a neutral character than a chaotic and/or evil society.
Definition 2.) Someone who believes the world is a metaphorical scale, with all actions affecting the balance between the various forces at play in it. Often, either the balance of all things in the world or the complete detachment from the world is the goal of these characters.
My question: How would one play this second type of character? As an example, if I were to play a true-neutral druid who believes in a system such as feng shui, how would I go about doing this? Would I have to take into consideration all of his actions, and then determine if they affected the balance of the universe in a great enough way that he needs to take steps to restore said balance? If he helped destroy the greatest evil in the world, would he then have to commit evil acts, in order to restore the balance between good and evil?