I used to roll this one all the time when I was a kid (but I also had a real paddle.) Some tips:
You can press the button to flip the teeter-totter. This is useful near the edges, where it might be impossible to catch a clown if you don't flip.
If the clown hits the edge, they will slow down.
You score 1 point foe hitting the teeter-totter, which is useful when trying to score '9's.
If you clear a rack, an 'X' appears next to the score to indicate you have a bonus life clown.
(I seem to remember that on a real system, you can swing the teeter-totter back amd forth with the paddle faster than the collision detection could determine if you hit the ground. Didn't try this with my mouse/emulator. If true, it would be almost impossible to lose a clown.)