It might be the shortest shot in the game of golf, but the putt can also be one of the most difficult. One of the reasons is that most players don't know how to read a green properly. Think about a book. Even a children's book can be nearly impossible to read if we don't know the language it's written in.
So, in order to putt well, we must know the "language" of the green. I believe that the tips below will help you read a green better.
1. Remember, any good golf course architect is going to try to deceive you. Keep this in mind as you start reading a green. If a putt looks like it'll break a little left, don't be too quick trust that thought...subtle breaks can be misleading. Use tips 2-5 below to confirm your gut instinct before you hit your putt.
2. As you approach a green, look around at your macro-level surroundings. Meaning, don't forget about the geography of the golf course. Maybe the entire golf course is on a hill or a mountain. It's easy to get so narrow in our focus that we forget these things. If a golf course is sitting on or near a hill/mountain, then chances are good that most putts will break down that slope.
3. Next, look at the landscape surrounding the specific green you're standing on. A deep bunker or lake/pond will often influence break. Those are low points in the terrain that will attract your golf ball. Depending on how deep those are, putts tend to break towards those features.
4. Once you've determined the general direction of the green based upon the geography, you're ready to investigate your specific putt. Look for contours in the green that would affect how water would drain. Are these contours helping or hurting the overall picture you discovered in the surrounding landscape? This will either magnify or reduce the break in the putt. Again, remember that an architect will often create conflicting pictures by using the areas geography and green's contours.
5. In some areas of the world, grain can have a huge impact on putting. Grain is the direction the blades of grass grow on a green. Often times, the grass blade will follow the sun, but it can also grow in different directions depending on how it was mowed.
If the blades of grass are growing away from you, it will be a slightly faster putt than normal. If it's growing towards you it'll be slower, if it's growing to the right it'll break slightly right, and if it's growing left it'll break left. Sometimes (specifically in the south), you can even look inside the actual hole and see that one side of the grass is "burnt out." This usually indicates that the grass is growing away from that area and it'll break towards the burn out.
If the grass looks shiny, that typically means the grass is growing away from you. If it's darker in color, that often indicates the grass is growing towards you.
Final bonus tip: 80% of putts are missed on the low side of the hole. That means that most players read too LITTLE break in a putt rather than too much. Try aiming 1/2 inch higher in all your putts and I think you'll see a lot more of them find the bottom of the cup.
If you start implementing these tips into your putting routine, I'm sure that you'll start to feel more confident on the green and make more putts.