The trick to getting an ace in Shufflepuck Cantina lies in timing, mallet placement and the ferocity you strike the puck with. As your opponent moves their mallet in readiness for your opening shot, wait until it's half-way towards the side of the table, then serve as hard as possible with the very edge of the mallet.
Hints
You can score an own goal. Keep this in mind before you move your paddle too far forward from your baseline. Straight, slow volleys will rarely flummox the AI. Send fast strikes into the corners for best results. The physics of real shuffleboard / air hockey apply to the game, as well. If you can ricochet a puck off of the wall slowly, you can thrust your paddle forward to hit it again before it crosses your half of the board. Use this to throw your opponent off and (hopefully) score a few points in the process.
Play as other characters
In order to unlock new characters and use their special abilities, you'll need to purchase all of their biography sections.