My method is a little different though no doubt it would have been utilized by many a writer whether they've been aware of it or not. I think in a very rpg style. That means that I mentally assign a set of attributes to each character as well as a corresponding numerical value to each of the attributes on a scale from one to a hundred. These scales and their assigned values dictate how the character reacts to not only the circumstances in which they find themselves but the world itself. Of course I create a detailed backstory that somewhat explains the distribution of the numerical values on the various stats within each character, though I do like to leave an air of mystery. 

Let's say that character A is talking to character B. The former has a lower charisma rating than the latter but a higher wisdom rating. You can see the dynamic that will form between these two hypothetical characters already. The former can very well be a nerdy shy type who can be genuinely nice as well as a fountain for sage advice. The latter can be likable but perhaps a little too self-righteous. It's almost like the characters write themselves.