One of the many mistakes that amateur golfers make is to under read their putts.
This means that on a sloping putt from either left to right or right to left, the golfer does not hit the putt far enough to the high side of the hole for the ball to run down the hill into the hole. More often than not, amateur golfers hit the ball too low and the ball misses the hole on the low side. On the other hand, professional golfers tend to miss more on the high side of the hole, always giving the ball enough room to roll down the hill into the hole. This is why the high side of a putt is often called the 'pro side'. This is no accident, there are two very good reasons why better golfers hit the ball up on to the high side of the hole.
1. The ball is closer when you miss.
If the golf ball is hit to the high point of a sloping putt and begins moving down the hill, it is always rolling closer to the hole. Therefore, even if it does not quite reach the hole, the ball is still tracking towards it with the slope of the green helping it all of the way. Conversely, if the ball is not hit far enough up the slope, as the ball misses the hole, the slope makes it roll further and further away giving a longer putt for the next shot.
2. The ball has more chance of going into the hole.
Imagine a golf hole on a big sloping green where the green slopes from right to left. Now imagine two golf balls, one sitting on the right edge of the hole (the high side) and one sitting on the left edge of the hole (the low side). If these two balls rolled across the two edges of the hole that they are sat on, one would have no chance of going in the hole, while the other has every chance of dropping in.
The ball on the low edge cannot roll up the hill and so cannot possibly go into the hole. The ball on the high edge has every chance of rolling down the hill, catching the edge of the hole and toppling in. Any putt on the low side will not go in, but any putt rolling across the high side may go in.
Do not be like most amateur golfers, instead putt like a professional, allow a little more break in your putts than you normally would and if you miss, make sure to miss on the high side of the hole because you never know, the ball may just drop in.