In thinking about changes it is useful to categorize what type of change is occurring. I generally use four broad categories. How are the physical circumstances of the character changed? This may include changes to their body (illness, injury, death) or to their material circumstances (wealth, social position). What changes occur in the character’s emotional and psychological life? The distinction is important. One may fall in love without becoming more loving; feel fear as opposed to becoming fearful. For example, a brave man may feel fear but a fearful man will seldom express courage. Finally what moral changes does the character experience? A brave man who becomes fearful could make several different moral conclusions: bravery is a foolish conceit; true bravery consists not of the absence of fear but acting despite its presence; that he is a weak man not worthy of respect.
Characters may make several changes in the course of a story but each change must flow from what was in place before. The character at the end of the story may be a very different person that the one at the beginning but these changes must – to make sense to the reader – be as a result of some event or interaction, some conflict and resolution. While in real life most of what happens seems random, in fiction, everything happens for a reason.
Once you have written out the arc each character must follow in their journey from whom they are to whom they become, you can lay them out on a sheet or a chart alongside the plot and chapter outline. What you are almost certain to find – especially if you have been doing the three things separately – is that there are places where they simply don’t match up. The events of the story won’t bring the characters they way you thought or won’t create the kind of changes you envisioned. You could try to mash them together and make them fit or you could let one creative process dominate the other two but I suggest that you instead engage in a dialogue with yourself. Asking questions about why and how can often improve both the plot and the process of character development and make your outline unfold in a surprising and powerful way.