Hah, I will take this as a test to see, if I have learned anything from this forum. First I have looked in my Oxford English Reference Dictionary, in which one of the definitions of technique is "a means or method of achieving one's purpose"
Mixing:
I have seen people say, that they start with the drums sounds soloed and then add the bass. Others start with the vocals. Others emphasize the need to use as little solo as possible.
Recording:
I guess, many people have basic reference starting points for mic placement.
Mixing:
I have read several times about people bringing reference recordings, which they listen to to learn how a monitor system (including room) sounds - so they can compensate for that frequency vice.
Recording:
To give or not to give singers reverb in the cans could maybe be considered part of a recording engineer's technique to get optimum performance.
To deal with people on a bad day may also to some include some hard earned "techniques".
Mastering:
If someone uses a multi-band compressor for dealing with insane bass frequencies not spotted by the mix engineer, I guess that would be/include a technique.
These where just examples to get things started. Because I think there is much more technique involved in much engineering, than this thread reveals. I am however by no means a pro, so this is all hearsay (hopefully useful for the discussion anyway). So I will now relurk