Well, I dunno if things like giving advice to strangers (both on the internet and IRL) really counts, but that's probably the majority of nice things I do for random people.
For more substantive things, I regularly give homeless folks a break. I have fairly common contact with them because I work security for an office building in downtown Portland, Oregon. Used to work weekend swing shift, but I recently got shifted to weekday graveyard shift, and both of those shifts cover time where it's common to find homeless people trying to sleep in the building's parking garage or other sheltered areas around the building. The way my employer says to handle them is to tell them to leave the property and nearby area (including the sheltered bus stops that are on the block the building occupies, despite them being public property), and if they refuse warn them that the police will be called on them for trespassing, then if they refuse again just fuck off and call the police non-emergency line to get them to come bounce the person off the property.
I take a bit of a softer approach. When it's raining and such and I find homeless folks camping out at the bus stops I just leave them alone because it's really public property thus none of my business as private security. When it's raining and I find them in the parking area or in other areas around the building, I tell them they have to leave the property and tell them that if they move to the bus stop then they're fine as far as I'm concerned. I've also directed a lot of them to a parking structure a few blocks away that I know has zero security presence on nights and weekends, because as bad as it might be to encourage them to trespass it's also bad to just force them out into the rain and tell them to fuck off.
Oh, I also sometimes give food to the homeless. Never when I'm working and find them trespassing or near the building, because I'd probably get into trouble for encouraging their presence instead of making them leave, but I pass by a lot of them on my way to my bus stop and sometimes I have food left over from whatever I brought with me for my lunch. On Wednesday this past week I had a couple packages of... apparently they're called
sandwich crackers, which I didn't realize until I just looked at a one sitting on my desk to decide what to call them. Anyway, I had two of them left over and gave them to a dude who was sitting on the corner with a "homeless and hungry" sign. That's also a pretty regular occurrence for me.
Honestly I don't know if I should really count these as random acts of kindness because they're more like regular acts of kindness, but hey, it kind of fits either way.