Here is what I like to do.
1) I put the engine on a test stand and use the fuel I intend to fly with.

2) Using 1/3 throttle and electric starter start engine rich.

3) If this is a new engine I will use manufacturers recommendations on break in.

4) After break in gradualy lean neddle valve to produce slightly rich run on high end. Remember fuel/oil mixture is intended to not only to provide combustion but lubrication and to carry away heat generated by the engine.

5) Slowly obtain the slowest idle I can get and still keep the motor running. This step I am using the throttle only, no low end carb adjustments unless the motor will not slow down at all. Most motors today are very close on the low end mixture unless your using a fuel mixture that is a lot different from most sport fuels.

6) A motor that is not broken in will give you fits trying to get it to idle slowly. A dependalbe idle is only possible after the motor is broken in in my opinion.

7) If the motor loads up and dies then adjust the slow end neddle in very small increments of no more than 1/8 turn. If the motor speeds up and dies then richen the low end by 1/8". Repeat step 5.

8) When the motor is installed in the plane I do not use mechanical throttle stop on the carb. I set the idle with the throttle trim on my transmitter. Then I use a throttle cut button or switch on the transmitter to close the carb stopping the motor.

The last few new motors I have purchased required less than a couple of low end adjustments to get a very reliable idle. Once you have completed the above when the motor is installed in your plane it should only require slight (a few clicks) high end needle valve adjustments to produce a good slightly rich high end even through weather changes. Should be no need to play with the low end mixture or at the very most should only need VERY SLIGHT adjustments during initial run.

Also make sure your throttle linkage is not binding or has slop in it. The servo must be able to transmitt mechanicaly the throttle motion from the servo to the throttle arm on the motor without loss of motion! If it does not then you will never achieve precise control.

Hope this helps, it works for me. By the way once I get my motors broken in and mounted in my plane(s) my electric starter becomes a hanger queen. I use a chicken stick and rather enjoy the challenge of getting a motor to start on the first few flips.