Here are the printed rules for the card:
When attacking a ship inside your firing arc, at the start of the "Compare Results" step, you may discard this card to cancel 1 of the defender's (evade) results.
My typical faux pas when using this card is that I play it before they are "done" modifying their dice. The issue is that it is to your advantage if they don't spend their focus or evade because they THINK they avoided all of your attack dice naturally. The problem is that I've had people kinda start to move on with the game after naturally rolling enough evades and then say "Oh, I wasn't done" when I try and use Crack Shot.
The issue is, during a normal passage of play, players don't typically look one another in the eye and verbally confirm (in unison) "and now we enter the compare results step."
Any suggestions from the community?
UPDATE 4/2/2018
I have applied some of the suggestions from the community to my use of the card. In particular, I played a match vs. a friend who was using an X/7 defender with a stealth device. He quickly realized that my 1 point card could shut down his 3 point card and would over spend on tokens every time the Crack Shot! ship would fire at him.
So, yeah. Keeping the Crack Shot! as a persistent threat that your opponent knows about is also a very good use of the card.
Thanks, InterWebs!
Edited by BDraftyUpdate 4/2/2018