Typically, if bent from a front end collision, fork will be bent backwards towards the down tube. I use a straight edge to measure this type of bent fork. If the fork is straight, everything should line up: the stem bolt, through the center of the head tube, through the center of the fork crown, and down the fork leg.

+1 To below, the straight edge test does not show side to side bend, which is pretty common damage wise as well.

Regardless of fork bend, learn to ID buckling/rippling of the DT and Top Tube, as that damage is often game over for the frame.