Golf is a very visual game. Many pros and high caliber players visualize their shots before they hit them. Techniques and tricks which help visualize shots can aid players, and help them lower their scores.
One way to help you visualize the line of a putt and keep your putter going on that line, is to mark a line on your golf ball and place the line parallel to the intended target line. Many top pros, including former (and possibly future) world #1 Tiger Woods mark their ball with a line for putting.
Marking the ball
Take a permanent marker and draw a straight line on your ball (upper right). That's it!
Along with a standard straight line, these accessories may also come with other alignment aids or markings to help you mark your golf ball.
On the green
If your putter has one (and most do), line the alignment mark of the putter head up with the line on the ball (below).
During the putting stroke, imagine the putter going back and through along the line, and the ball traveling on that line after contact. If you've read the break correctly and lined the ball up right, draino!
If your putter does not have an alignment mark, you can draw one with a marker on the top line of the putter, or even just a small dot.