Making Strides
It doesn't make sense. Golfers of all skill levels want precise distances on their approach shots-down to the exact yard-but when they reach the green, they simply eye up the length of their putts. And this is where distance matters the most. Trouble is, there is no obvious way of measuring distance on the greens, nothing comparable to marked sprinkler heads in the fairways.
This is where it all starts. Select a hole in a flat area and pace off 10 steps from the cup, placing a ball down at every step. When you finish, you should have a line of evenly-spaced balls, starting about three feet from the hole and ending about 30 feet out.

Starting with the nearest ball, try to roll each putt over the front edge of the hole. When you finish, replace the balls and repeat the drill. With some practice, you'll develop a feel for the tempo required to roll a ball one additional stride. In time, you'll have a stroke for putts of every length, simply by thinking in terms of your stride. Then you can easily pace off putts on the course and fit them to the system you've created. Better yet, the system is adaptable by simply adjusting tempo based on green speed. Your stride is still your stride.

Gauging distance on uphill putts usually requires adding a stride or two to however many you've paced off. In the photograph here, I have a 15-foot uphill putt. For me, that's a five-pacer, measured by the balls placed just outside my line. But to compensate for the upslope, I play it like a six-pacer, indicated by the extra ball placed a few feet past the hole.

This putt also breaks right to left about eight inches, but I'm still thinking about rolling the ball like a straight six-pacer; I just aim eight inches out to the right. Because I'm confident in the pace of my putt, I can easily determine break. I know the slope will take the ball to the hole and will take about one pace off the speed.

Putting downhill, you have to subtract a stride or two-perhaps more if the greens are fast-from the number you've paced off. Here I have another 15-foot putt, with about eight inches of left-to-right break. This would be a five-pace putt on flat ground, but to allow for the slope, I imagine it's a four-pacer. Notice how the ball marking my last pace is one pace short of the hole.

Like the uphill putt, simply play it like a straight putt, aiming eight inches left of the hole to allow for the break. Use the pace system to determine the effort required, but don't think of any putts as big breakers; play them straight, just adjust your aim.
Tier to Tier
As a rule of thumb on two-tiered putts, add or subtract the number of paces you step off on the actual hill separating the tiers. For example, if you take two steps on a downslope that bisects a 10-pace putt, play it like an 8-pacer. The reverse holds true for putting uphill over a tier: I would add two to my pace count and hit it like a 12.

But before you consider all the possible variations, develop a feel on the practice green for flat putts from one to 10 strides. Once you do, you'll find this system an excellent starting point for simplifying every putt you face.