When it gets down to the basics, ask yourself if the person performing the action set out that morning with the deliberate intent of killing noncombatant innocents.

Granted, there are gray areas. It can get too easy to "overlook" innocent people in the area of a legitimate military target if you are motivated enough. IMO, Israel has done this in a number of cases. But they have never had a planned policy of deliberately killing a large number of innocent people in an uninvolved area. The PLO has, or at least organizations under it.

Also: Remember which sides of the current conflict "human shields" work on, and which ones they don't. And why.