The rules aren't very intuitive, but pretty simple once you get them: you just accumulate points and must not reach 30 or above.
You play one card each turn, and at the end of your turn should draw.
Spades remove 20 points, queens and kings pass your turn, and kings make you draw 2 cards instead of one.
The trick is that when the pirate is distracted, he doesn't know where you picked a card from, so the only thing that matters for him to find you cheating at this point is counting if you have the right amount of cards.