I did okay selling some of my old junk on eBay. I think the main thing was that I was very upfront about any blemishes or scratches on anything. Taking closeup pics of the problem makes the buyers trust that if you think every little thing is worth noting, then they have faith that your are being honest. And have some humor!
My very first sale was for my grandmothers old curtains. I titled it "Ugliest curtains in the world".
I included the story about how these had been hanging in her house for 30 years, and had an enormous and unpleasant print on them. I added that if anyone thought they could make them into an equally hideous Halloween costume, they were wrong because the fabric felt like steel and was very scratchy to the touch. Oh, and grandma smoked like a chimney - but they had been cleaned and I couldn't smell any trace of smoke on them.
I find that including something personal in your listings makes them sell. When I sold a bunch of my books for a certification, I said "I've already underlined and highlighted the important parts for you!"
After a while, I got sick of the shipping and made everything "local only" and pickup only. Don't ship books. Not worth it. Just list them for local pickup only.
Of course I didn't think I would get any takers! I was just testing out how the process worked! Low and behold, someone bought them for $15!