It really depends on what type of flying you are doing as to which end (high / low) you need to adjust. If you fly mostly full throttle then it would be your high end needle you will adjust. If you fly mostly 1/4 to 7/8 throttle then the low end is the needle that needs to be adjusted.

Plug color is as follows:

White / Gray is lean.

Tan / Light Brown is perfect

Dark Brown / Black is rich

The way i tune mine is to get the engine warm and then tune the high end untill the rpm drops then back it off untill you reach top rpm and crack it back untill you loose another 100 rpm. Then go to the low end and tune it untill the engine stumbles when going from low to high at quick pace. Then back it off untill you lose the stumble. Then re check the high end again. It doesn't take much of a turn either the needles are very sensitive. I run mine with 50 to 1 Belray MC-1

Jim