I'm on a long term decluttering plan, I have an item or two for sale on FB marketplace pretty much all the time. This is small stuff from around the house that's no longer needed so it doesn't matter a whole bunch what I get for it. Or it's used doors, appliances, etc coming out of the renovations I do for a living. Usually put it at about a third to a half of retail so it moves fast and easy to politely but firmly refuse lowball offers. My best strategy is not to give the item's precise location until the prospective buyer has agreed to date and time to meet. Seems like a small thing but at that point the buyer has made a form of commitment. Started doing it this way to protect reno clients who obviously wouldn't want it known that 1234 Smith St was in the middle of an empty home renovation, but I realised it makes a difference with all the sales. Having to agree to be somewhere at a certain place and time seems to make the tire kickers smarten up a bit.
My advice to those working on purging out the junk is don't put up items for free. You might get rid of the item quickly, but not before you have to field a zillion "is this available" messages, requests to hold, and other general fuckery. Put the price at something nominal, $5 or $10. Gets rid of 80-90% of the idiot calls/messages.
Along the same lines, ads with multiple items for sale are a pain to maintain and get confusing quickly, easy to forget who you're dealing with and which item you're discussing. Online ads are free, take a few minutes and do separate ads for each item. You'll probably net more money as a result, and it's a lot easier to maintain. Yes, it will take longer to move everything. If you want to blast it all out at once, there's always the tried and true garage sale followed by a trip to the dump or Salvation Army with unsold items.