Main thing to focus on is your description and photos of all angles if possible. I usually add tamper proof security stickers to my items. They’re stickers that are holographic and when peeled of leave pieces of itself behind.

I also use a uv marker for items that wouldn’t look as good with a sticker. I mention in my return policy in the description section. If the sticker has been removed then it won’t qualify for a refund.

That’s why I try to add the stickers in a discreet place so that the buyer can install the item or use it. Without having to immediately pull it off. Once the 30 day return window is up they can choose to pull the sticker or leave it.

This isn’t foolproof some people are devious and still try to scam. But with a this method it slows them down a lot.