Any slope is going to be from right to left on that hole. So I take that into account on every putt I hit. If the course is relatively flat, go to the pro or course superintendent. Ask about nearby reservoirs or, failing that, the area's lowest point. Find out where that point is and take advantage of gravity.
Gravity is a wonderful concept.
After you know the lowest point, look at each green in detail. If you're on an older course, the greens probably slope from back to front because of drainage. Greens nowadays have more humps and undulations than ever and are surrounded by more bunkers. And the sand is the key. The drainage should be designed so that water runs past a bunker and not into the sand.