Chart the grain on your home course greens. It may save you several strokes a round later. Take a small notebook with you and look at the green from all angles in the early morning or afternoon sun. Depending on how high the sun is you may have to squat down as low as possible to see the grain.
The noticeable sheen you see means that you are looking directly down or with the grain. Putts hit with the grain roll more smoothly than against the grain but, more importantly, they roll further.
Draw a rough outline of each green in your little notebook and indicate the grain direction with arrows. You can also indicate major and minor slopes and rises at the same time. Both these pieces of information will come in handy later in the season.
Grain results from the fact that in any specific location grass grows in a specific direction, just like the hair on your head. As the blades grow they all bend in the same direction and provide appreciably less resistance and friction to the roll of your golf ball putted with the grain. Putting into the grain, however, your ball encounters the ends of all those grass blades head on making for a lot more resistance and a much slower putt. Looking up or into the grain, seeing what your ball encounters, the grass appears much darker than when looking down grain.
For those who doubt the importance of grain I suggest an experiment that can be done on the course or the practice green.
First, find a level area on the green and determine the grain for that green. Second, place a tee in the green about ten feet directly up grain from the hole. If the cup was not cut on a level part of the green then just use two markers ten feet apart aligned with the grain. Now, (third), putt four balls up grain from the hole or first marker to your tee. Step four is to use the same stroke (same force) and putt those balls back along the very same line to the hole from the tee position. In most cases three of those balls will run past the hole as much as 4 feet. That's a difference of 40 percent. That's significant.
If you reverse this experiment by putting your 4 balls down grain first your putts back will nearly always be well short of the hole. Putting across an unseen grain often accounts for mystifying breaks that cause our putts to drift off line. Grain running across the line of our putts can cancel a slope break or, even worse, augment an obvious break.
Most golfers can read the line of any putt reasonably well. Putts stroked too firmly generally only miss the hole by a few inches as they go sailing by.
Comeback putts are even more difficult and frustrating. The point is that more putts are missed as a function of distance rather than direction.
Since putts count for two strokes a hole at par they are too important to be taken lightly. Zeroing in on distance is the best way I know to eliminate those three putt greens. Too short or too long can be seriously affected by our knowledge and feel for the grain.
Learn to read the grain and you equip yourself with another valuable tool with which to attain lower scores.