“If you want to understand someone, you have to look at their world from their point of view.”

“Or walk a mile in their shoes…”

Well…it might help but it doesn’t get you even halfway there.

Understanding somebody’s action takes two steps.

The easy part is assembling the data base from where that somebody has started to make the decision/action you are trying to understand. And you can indeed do that by following the advice above.

And here comes the tricky part.
You might try to interpret that database as yourself. “What would I do if I were in his place?” is a very interesting question but by answering it you only widen whatever understanding you have about YOURSELF.
If you want to really understand somebody else you need to understand his way of thinking, it’s not enough to find the ‘motives’ that have prodded him into action.

Of course it’s practically impossible to ever get an accurate estimation but the simple exercise of honestly trying to think AS somebody else and not merely ‘in his shoes’ will help tremendously.

Some more advice on the subject: http://www.scotthyoung.com/blog/2007/08/28/the-critical-7-rules-to-understand-people/