I start with the high and tune for maximum RPM then back off 1/16 to 1/8 turn. Then set the low for the best transition. More or less keep closing the low until the RPM's drop then go back to the drop point and open it a 1/16th. Fly the plane and then make tiny adjustments from there as needed. Many opinions on this so do some searches. This way works for me perfectly so try some different things and stick with what makes you feel good about the process. Also check the manufacturers pages for even more ideas.