First make sure there's no crud in the throttle plate area, and that the throttle plate is firmly attached to its shaft and can't go cockeyed. Everything else must be done with the motor fully warm.

Turn the throttle stop screw out so the throttle is completely closed. Make sure the cable linkage has a bit of slack in it and isn't holding the throttle open. Turn the stop screw to the point where it just barely starts opening the throttle, and then 1/4 turn further.

Start the motor and adjust the throttle bypass screw for the desired idle speed. if it still wanders, adjust the throttle position switch (which I'll describe separately upon request).