Here's a really simple tip to get your putter square to the ball on impact. Get a string, a couple pencils (they need to be a bit longer than the one you use for the scorecard. Just plant one behind the center of the hole and another a few feet away. Then add string.
Your putter head will go slightly inside to square to keep the ball on track. Very visual. Very easy. A very good way to keep putting practice on track!