Well, in my experience of ebay, I would look at the feedback score of the seller first, then the percentage. If his percentage is below 98% then I will look at the feedbacks left by the buyers.
The other important things to consider are,
1. Read the item details and bidding policy mentioned by the seller very carefully. Because a ebayer's can consider a price tag of an item with adding the pakaging and postage.
2. The second thing is to see, if the seller have already added the VAT in the items price or he will add it at the final price including postage. That means, VAT will be added on top of item's final price+P&P.
3. The third things is, if the seller is forcing you to pay the postal insrance. which you should check before you bid. Because sometimes it could be quite unexceptable. Some sellers mention that the postal insrance is optional, thats fair enough. The items shipped from Far East normally have mandatory postal insurance.
4. The fourth and last thing to consider in my opinion is the postage time. You should know that how long the item going to take to get to your door step. The items shipped from outside the United Kingdom can take upto 2 weeks.
I hope this will help to shop on ebay.