Putting is not an exact science and as Joeyola correctly pointed out it's basically all about feel and practice, lots of practice. That said, you can try this rule of thumb that I use when putting on very fast greens (forget about club movements): take the putter distances at face value, i.e. if you ball is 7.5 feet (more or less) away then hitting it halfway (more or less) through your 15 feet increment (if your putter has one) should make it. If the ball is 15 feet (more or less) from the hole, you could either go for a 15 feet increment full strenght (little bit less for a 14/13 putt) or opt for halfway (more or less) the 30 feet increment, although the former option will make the meter move faster. And so on, and so on...you get the point. Of course, for every inch up or down in elevation, add or subtract a bit to the putt.
Keep practicing and good luck!