Hello, I have sold over 1,000  items now and can tell you when your just begining selling on Ebay, you may find this guide helpfull as it comes from my personal experiences.
  The biggest thing you can do to save from getting Negative feedback is:
1. If you sell something..and a customer has a problem and addresses you with it....Be open minded and Be honest, Be quick to answere E-mails and be Sincere..I List that I do not give refunds, but on individual bases..I see I do make mistakes from time to time, and that most buyers just want fairness..so even if they come out threatning your feedback, tell them you are willing to resolve it to make both of you satisfied. If something small was not mentioned in your auction yet they found it like a stain or missing button or something....be quick to offer a small refund:) it may cost you 3 or 4 bucks but its worth a mutually good experience.
 And follow through..offer partial refunds, or discounts for the future...
2. Another way of handling issues before they happen is Always get delivery confirmation, add the 55 cents to the shipping amount..so even if they dont take insurance, you can know if they recieved it or not..if they are telling you they didnt.
3. From time to time I made big boo boos ..like shipping items to the wrong person..The Biggest thing you could do here is find the contact information on the customer...Call them on the phone,..dont e-mail them and be real, tell them who you are and what its in refrence to...and explain you made an error and its on the way or you will refund there money if they dont wish to wait, You will find they will wait and glad you called them:)..and the person who has the wrong item have them forward it to the right person and follow up to make sure all went well....thank goodness this only happened like 3 times in 800 sales...but I got positive feedback for those auctions:)..
4. Calling customers through their contact information..( which is available to you through Ebay)....is the best way to resove something before it gets carried away.....because calling someone and speaking to them live is more Sincere then any E-mail.
5. You can find contact information by clicking  Advanced Search>Under  Members' Find Contact Information link on left side of page>place information in boxes and it will be sent to you..
5. And most importantly state your policies in your Auction..and remember your a customer too and treat people as you want to be treated:)..Happy New Year to All...and hoped this helped:)..And Good Luck Selling on Ebay!!