Pass by sloppy or no pictures or descriptions - their care of the item and packing may be just as bad.
Pass by reams of waffle in the description - should not be needed to sell.
Pass by fancy fonts and colours - pretentiousness may apply to the description of the item.
Pass by "Collection only" and location "UK" - you should not have to ask them where on earth they are!
Applicable only to some old electrical items: Pass by "I switched it on it works/doesn't work"
Pass by "Don't know if it works - haven't got a battery/mains lead". cf "Cannot test car as haven't got a key"
Pass by no mention of make or model.cf "Car for sale - it is a blue one"
Even with that lot, I do buy items from eBay!! Like this.
And I sell some.