Spare shooting is definitely an art that each person has to develop their own system. In general, the best spare shooters do a few things...they throw it straighter so they can take the lane out of play. Also, they aim at their spares in a way that they can still miss and make it. Meaning...if you tend to always miss a spare a certain direction, change your system to aim in a way that you can still miss a little and have a chance to make it. Another important thing is you HAVE to practice them!