Great question, as I personally believe the best confrontation is the one that is completely avoided, which we can have only so much control over.
Gas at night: not generally. And never without checking out the whole area first - regardless of daylight.
Locked doors: Always - in house, home or not, and always in my truck - soon as I step in. It's just easy.
I don't buy or pick up newspapers - get my "news" online mostly, and I have a PO Box, so I have to disarm going in - but I still check out the Post Office before going inside. (The lot is generally empty when I'm there anyway.)
Driving - especially at night, and most especially in "the city" - I always try to leave a gap between the nose of my truck and the vehicle in front of me at a traffic light. I'm always scanning the area at traffic lights, and do my part in ensuring I'm not completely along side another car... I like to see "them" without them so easily seeing me.
In public, I always maintain a "bladed" defensive posture - but in a casual manner (e.g. in line at a check out lane). My strong-side elbow always hovers over my CC gun, so I do most transactions left-handed on purpose.
So much of this is just "second nature" from doing it so much, I'm aware that I'm doing these things and more, but "better safe than sorry" kind of mindset, you know?
The group or gang of trouble-makers - that would have to be completely situational. If they're directly in my path, say near my vehicle, I may consider watching and waiting while sizing them up. However, if I can easily navigate around them, I would without a second thought - though still watching my six. The "cop" in me still has to take a back seat to more sound reason and logic, because I'd otherwise walk right up making eye contact, "reading them" up and down and speaking very loudly and clearly directly to them... not always the wisest approach, though generally effective in sending a message.
How about you?