almost 3 years ago - Crater Creator - Direct link
If I have a reasonable amount of inventory space free, I'll Take All indiscriminately on any regular loot containers - trash piles, cabinets, sports bags, that sort of thing. I do take note of the items I'm collecting, though. As I start getting full, I'll start scrapping more and more things, starting with pipes and nails, and consuming food & drink if I could use the fullness or hydration.

If it's a tier 3 POI or higher, I'll probably accumulate more than a backpack's worth of stuff. So I put a chest on the street, close to the entrance. I dump everything that won't be useful while I'm questing, before I start. For big POIs, I'll make several trips back to dump stuff off at the chest, whenever I swing by that side of the building in the process of clearing it.

Edit: If it's a tier 5 and I'll definitely have to spend the night in the field, I may upgrade the chest on the street into a little processing shack. I just put up the bare minimum of 4 walls and a door, so that I have some time to defend myself if zombies come. I make a campfire and, if I can slap one together, a forge. I make drinks with the campfire, and use the forge to turn anything I can into bullet casings, bullet tips, and forged iron. It's all in the name of reducing inventory, without taking the penalty for scrapping.

I don't bother leaving signs of whether the POI is looted or not. If I wanted to check, I'd go to a loot container just inside the entrance and see if it's reset. Probably 85% of the time I'm looting a POI, it's for a quest, so I know it'll be fresh with loot.

Once I consider myself in the late game, I'll loot toilets and garbage cans progressively less often. I slow down a bit when looting containers that can have more unique items - safes obviously but also lower-quality containers like nightstands and clothing piles.

When I'm with it enough to plan ahead, or I get lucky with a nearby vending machine, I'll carry around an Eye Kandy, and then try to leave a couple of the highest concentrations of good loot containers unopened until the whole POI is cleared. Then I pop the Eye Kandy and scurry around, hoovering up the good loot (often throwing out lesser items because I'm out of room by that point and was too lazy to go back to my dump chest).

Similar to the Eye Kandy, I'll reserve space in a chest back at base for stuff I don't need and want to sell. Then I'll do a trader run, stuffing my face with anything that'll increase my barter level and zipping through as many trader inventories as I can before the effects wear off (I can comfortably hit 3 traders on 1 Sugar Butts in my current game... really need to get a motorcycle). Outside of prepping for horde night, using those candies is when I'm most motivated to squeeze the most out of every second.