If you've read Sherlock Holmes, you likely recall his supposedly paying attention to all details around him, like how many steps were in the staircase. That seems mostly unnecessary[1], and 'all' details is bunk/impossible... but I am building up a list of things to try to be more conscious of, whether for personal utility or good citizenship. And a recent afternoon where I kept an eye out for bike racks, in an area I've been up and down multiple times since March, and discovered many racks I had been totally unaware of, highlighted how much difference conscious attention can make.
Accessibility: can wheelchairs get around? This is largely a 'good ally' thing for most of us, but also of personal import to me since I started bicycling again, often on sidewalks. (And of course I still have it easier than a wheelchair: narrower, bigger wheels, and the option to walk or to take the street at speed.) At any rate, I notice un-ramped curbs, and obstacles, that I might not have before. As a tangent, non-bikers could also see if bikes can get around safely: are there protected bike lanes, or wide sidewalks?
Trashcans: are there public places to put trash, or do you have to sneak it into someone's dumpster, or carry it with you to avoid littering? One notices this when one actually has trash, but keeping an eye out otherwise can be useful.
Drinking fountains. Something I took for granted, at least in public parks, until I came to Philadelphia.
Benches, or public ledges. Something I didn't even think to expect, until I stayed in Montreal and started to run across random benches, and even picnic tables, on city streets. And then the covid pandemic and my only getting take-out, makes me more aware of "is there somewhere to eat what I just bought?"
Bike parking: is there any, and does it not suck? (Does it allow U-locking the bike frame.) If you don't bike, well, looking out can be your allyship.
Public shade: are there public spots where someone can take refuge from sun or rain? Are there shaded pathways? (Probably not, unless the street trees are very good, but read about the five-foot way to see what you're missing.
Building shade: are buildings a direct and energy-expensive war between sunlight and A/C units, or is there shade from trees, awnings, overhangs, balconies, or shutters?, to block unwanted sunlight? (I don't count curtains or interior blinds; those still allow the window to become a radiator.)
Speaking of which, do taller buildings have balconies, patios, decks, allowing residents (or office workers) to get outside without having to go downstairs (or, for apartment dwellers, having to get their shoes and keys).
Bollards. Are pedestrians, or buildings, protected from out of control cars? Consider how many Japanese streets are lined with steel or concrete, or intersections in Mexico City
Are there people walking around? Or biking? What kind of bikes? Are people wearing helmets? Do the bikes have kickstands or baskets?
[1] Although, if you might take stairs in the dark, knowing how many steps there are is useful. After, in lieu of my candle experiments, I started trying to minimize bright light at night, I also counted the steps down, and it has served me well.