I'm not a professional ebayer, but I've used them on and off for 15 years and a few hundred transactions. Right or wrong, these are some of the guidelines I follow to minimize headaches to me.
1. No shipments outside the US. I don't want to fill out the customs form, I don't want to deal with the problems arising from customs delays, I don't want to deal with buyers that "didn't know" they would get hit with hefty import duties/taxes. Now I'll add tracking problems to my list, although this underscores a bigger problem with USPS.
2. If the item has enough value that I don't want to be on the hook for a lost shipment, insure it. If the buyer never receives it, I lose.
3. USPS is quick and integrates well with ebay, so I can ship things out quick with a minimum of fuss. Their package tracking is better than it used to be, but nowhere near acceptable in my view (even for domestic shipments). Small packages are cheap to ship. But good luck if you have an issue that needs to be resolved, including filing a claim for a lost (insured) package. Choose your carrier wisely. I basically self insure with USPS. If I'm not willing to eat a loss, they are not an option.
4. I've received more than a few priority mail boxes and envelopes over the years with the corner ripped clean off. It seemed evident to me someone tried to quickly empty some or all of the contents without getting caught. I now zip tie the item to a large piece of cardboard to prevent anyone from fishing the contents out of a small hole. I've never had this issue with Fed Ex, and only a few times with UPS, but it was related to the shipper using weak cardboard, poor taping job and a dropped package causing the damage, not necessarily an obvious theft attempt.
5. Larger or more valuable items can be restricted to local pick up only. I've been surprised at how effective this is, and ebay is much more convenient than dealing the craigslist people. Of course I live in a metro area and an overpopulated one at that, so YMMV. I've also bid on local pick up items thinking I would get it for a steal since I'm not competing with as many buyers. Not really! The items still got bid up to "fair ebay market value"!
Ebay isn't exactly perfect, but for me there is no substitute when it comes to clearing stuff out of my house and getting money back in my pocket. USPS is cheap, but there are better options. In my view they never really had a customer first company culture.
