Ok so we all want good feedback, this is a successful way forward on eBay. Unfortunately it's not always that easy, theres always someone out there that will leave bad feedback even if the product was fantastic and not even faulty. If you do get bad feedback its best to respond in a positive apologetic manor and see if thingscan be resolved. This looks far more professional than getting angry.
The best way to get good feedback as a buyer is to pay promptly through eBay as soon as you have won the bid.
The best way to get good feedback from a buyer is communication, make sure you mark the item as sent, once sent, email the customer to inform them the item is on its way and leave them good feedback. Send the item quickly and wrap it up well especially if its breakable.
Prior to this, make sure the item is described as truthfully point out if possible, any marks, scratches on it. Upload as many pictures as possible.
I have sometimes collected items and they have had a tear in. I pointed it out to the seller at the time, you may get some money off.
If there are any problems, make sure you contact the customer to try and resolve any issues as soon as possible.