i use a modified 3,6,9 rule, after using it awhile, you find it may be 2 1/2 boards, or 7 etc. i use the same ball for both strike and spare shots. for the 7, or 4 or 6 or 10, i move way over, flatten my hand and straight wrist and throw straight. for 'stuff' left on the rest of the deck, i use my strike shot, but move my feet the required amount of boards and use the same strike target.

I went in today and and gave the '3,6,9' system a try (I actually had to Google it to see what it was; never heard of it). It was working pretty well for me, though I had to make a few tweaks to it. One was for 6 and 10 pins (I ended up going straight at those). Another was for stranger leaves (like that 1-2-4-10 I seem to leave once or twice a series). For the run-of-the-mill stuff I usually leave (and miss), it was working out well. Thanks for the tip. Hopefully that carries over to league and helps with the average.

I throw my plastic ball at everything. It goes relatively straight with very little rotation on it.

I think one thing that gets overlooked is your time taken for the shot. A lot of times bowlers will rush spares or not be in the correct frame of mind to pick up the spare. So my word of advice is to relax, settle in, and take as much time on your second shot as you do on your first shot.

When I use plastic for my spares (except 6-9-10 pins), I will line up the shot by seeing what boards the pin is on and follow those back to the foul line. Then I do a 'dry swing' with the ball to make sure my swing is on target with the boards the pin is on. With that, I just put my feet together in starting position and my swing is already in line. So long as my swing remains straight and my release is ok, it should get the pin.

Remember, except for 7 & 10 pins, you have almost 2 feet of target area for a single pin.

PS. I actually choose the boards on the right half of the pin because I can get a bit of hook sometimes.