Mixture leaning and EGT gauge
 

Can someone advise me on how to use the EGT gauge to ensure that the engine is correctly leaned (mixture not degree of bank!).

There is a 'red' indicator on the EGT gauge that can be manually rotated - I have forgotten how to use this!

Current method is to pull out the mixture knob until the RPM starts to drop and then move it in a fraction to restore the original cruise RPM.

Also at what height should you lean the mixture for most economical flying. I tend to do it above 3000'.

The aircraft in question is a Piper Cherokee 180C.

Thanks