What should I be aware of so as not to fry or damage the ECM and other electronics while working on my car..?

[AylmerQc]

I learned auto-mechanics from working on 60s and 70s cars although I did have a couple of 80s Volvos some 20 years ago.
I recently bought a 2007 XC70 and I'm taken aback at the amount of electronics (Can newer cars have even more?).
Browsing and researching different threads I've seen it mentioned that connecting the battery, if not done "correctly", can fry the ECM.
There were no specific details given, although we should all know to disconnect the -ve terminal first and hook it up last. There was a video showing hooking up a battery minder first before disconnecting the battery, which I hadn't thought of doing but will in the future.
So, what should I be wary of doing and definitely not do to prevent damage to the ECM and other electronics on my car?

[abscate]

I think this is folklore creeping into the internet. Volvo tells their techs to install the battery with the key in and turned to key position II I think, but this is to prevent them from getting hurt by a spurious air bag deployal. I’m not sure if this really happens or if it’s just a liability thing.