This is my basic take on feedback, and what to do to try to prevent negatives.
As you might see, up until now, I've been fortunate enough to retain 100% positive. No negatives, no neutrals.
I'm nothing special, I just look after my customers - or try to!
I leave immediate positive upon payment. I do this because, I list all of my terms in my auctions. I offer help, and advice if buyers need it. I also ask them to email me, if there are any problems with paying - this way we can sort something amicably, and they can "hopefully" leave an honest positive pertaining that I am helpful - even if the sale cannot be completed. Another way to think about this is also, that buyer had completed their part of the transaction - its only fair. Don't forget, feedback is purely voluntary. No-one needs to leave it, it is not compulsary.
Do not chase up feedback which hasn't been received. There are multitudes of reasons for this. The buyer just doesn't realise they can, or "should" leave feedback for the buyer. The buyer could be waiting for their feedback from the seller (because they've completed their side of the deal in their eyes!). They could be unhappy, but frightened to leave neut or neg feedback in case its reciprocated! The latter is the reason I leave the buyers first.
Granted, we all have the odd "mad" buyer, who will leave an unwarranted negative - all you need to do then, is use your reply carefully and calmly state a small explanation. Any buyer with any modicum of common sense, will realise this was an issue which could have been resolved. Any undeserved comments on a sellers feedback, left for a buyer, are viewed by most with fear, literally. Not being calm in response to feedback you don't like, shows an impulsive nature. Its always best to show a steady approach to your dealings.
Personally, if I get a comment I don't like in a positive, I just leave it and don't reply, rather than draw attention to it by adding an extra line!!
If you get a neutral don't! apply for a withdrawal! They look like negatives once they've been withdrawn AND! they soon disappear off the page. More importantly, they DO NOT EFFECT your rating!
Most importantly, remember the fact that feedback is your face on eBay. It is what people look at first, and something which we need to maintain to keep status on eBay. Its imperative for a powerseller to maintain a certain level of feedback, and any other sellers wil always benefit from a good feedback record aswell, obviously. Using your feedback correctly, can benefit you in more ways than one - I'll add to this in another review!
See my other reviews, selling, features, and even postage advice is in there.