Putting green practice before a round is definitely the way to go. Make sure you get a good feel for the green speeds like mentioned above. I also practice the basic lag putt. 5, 8 12, 20 feet, make sure I can get within a foot from every distance, or darn close to it!!

Your putter, may not be right for you. Is it too light? I found that when I use a lighter putter I simply CANNOT figure out distance.

I went to a Rife 2-Bar Hybrid this year and I've probably saved 3 or 4 strokes PER round I've played. Its a great feeling putter (I use the heavier weights).