SURVEY !!! ABS/ETS/ESP problems on ML's ?

[Mike_ML320]

Hi there to everyone !
After reading quite a few messages on this forum I noticed that my problem with the ETS/ABS lights coming on is anything but a "Rara Avis" for the ML owners and I have the feeling that there must be many others that went through some similar problems.
What I am trying to do is to come up (following your input) with some common-sense step by step troubleshhoting procedure for this kind of problem and hopefully it will become a main reference thread for newcomers.
So lets say someone who believes in the saying "If it ain't broken, don't fix it" and/or who thinks that finding some underlying issues before replacing a $1,600 ABS/ETS unit may be worth spending some time, wants to start with checking the simplest thing first and then progressivelly go to the more complicated ones. What would you think the order should be ? (i.e starting with number 1, 2, 3,...and so on. I heard break light switch, K25 relay, bad soldiering contacts,... .
Also, like I said feel free to share any weird simptoms and temporary or definitive fixes you found.
Thanks a lot!