Ideally, I want to sell whatever items the animals are requesting that day, because I noticed that whenever the animals want something, that item will be in low stock for the next 3 hours & none of my friends will be selling them unless they were uploaded 3 or more hours earlier, leading me to believe that we all get the exact same scripted item requests & they are not randomly generated.
Anyway, I can never actually do that because I'd have to spend forever waiting & farming, so I just sell things in sets of 3 at the lowest possible price once I have more than 7 of something, except fruit; I hoard that. I noticed that apples, pears, peaches, squid, flounder, carp, mackeral & bugs sell well, & that coconuts, oranges, cherries, shells, coral, & anything rare sell poorly, even at the lowest possible price.
About half of my friends only sell rare items at high prices, & no one ever buys them because it's not worth it; the next time you see that animal, he's not going to want the same item, & the reward he gives you is not worth spending the bells to buy it. Well, I have noticed that this tends to only happen with people who just started playing. They'll catch on eventually.
I try to use the sales boxes as an indication of inactivity; If a person hasn't put something to their box in 7 days, I delist them, assuming they got bored with the game.
