I found that a good starting point is to set both high and low screws at 1 turn out. aka. remove plastic caps (red and white usually), turn screws clockwise until they lightly "seat" then back out (counterclockwise) 1 turn. This is usually a good starting point. Also I like to leave them alittle rich for the fact a saw runs different once under load and temp is usually colder outside. A saw with alot of use or lower compression will usually need @1.5-2 turn out on the low speed due to the fact the engine can't develop the low pressure or "sucking" force through the carb at low speed as well as a fresh/new saw.