Mounting cartridge in Eminent Technology ET-2 tonearm

No this is wrong - if you level the platter, and then alter the TT feet to level the ET tonearm spindle then the platter would now be out of level.

You level the platter, then level the ET using the 2 pillar screws at the base of the ET arm.

I disagree.  My method uses the spindle as the measuring device.  If you make the pillar perpendicular to the platter and the spindle parallel to the platter and do it precisely, your platter will end up being perfectly level when the armwand does not move inward or outward when bounced.  This is a far more accurate way to level the platter than using a bubble level.

I just referred back to the manual and this is exactly how the procedure is described.  I guess that's where I got it from many years ago.

@ketchup 

I have set up many ET's - on some the spindle can go out of level when VTA is adjusted - in your terms of reference it would then not be parallel to platter.

I check the spindle is still level every time I change VTA to be sure everything is level.

Some bubble levels are quite good - I use the one supplied with my Naim Aro and with the bubble in the centre by eye, it meets or exceeds some quite expensive electronic levels. Using the Naim bubble level and then checking the level with both a Rega,Cartridge Man level and a commercial Starrett yielded no further improvements - the error from the bubble level was below what the electronic levels could measure ( they all read 0.000000 ). That actually surprised me when I checked it. I had expected the electronic levels to pick up some error.

Azimuth will affect channel balance. To adjust precisely I use a test track, 1kHz sine L+R, and an oscilloscope to adjust azimuth for equal channel output. The test track is side1 track1 of Analogue Productions "The Ultimate Analogue testLP".

Actually, by my measurements and according to internet sources, azimuth has a very minor effect on channel balance and probably ought not to be used as a method for correcting imbalance. It’s best used to reduce crosstalk between channels.