CHECK VALUE - To give you an idea what price to start your auction at, check in current and completed items to see what price the item sells for.
STARTING PRICE - A lower starting price is always better as people seem more willing to start the bidding. Out of two auctions for identical items valued at $100, one is started at $9.99 and the other at $100. 9 times out of 10 the lower priced auction will finish on a higher price. If the item has a high value start the auction at a low price and put a reserve on it (at the price you're willing to sell).
FEES - Check out the charging system run by eBay. You are charged a percentage of the starting price and the end price. The percentage changes in stages which start $0.01-$0.99, $1-$9.99, $10-$24.99 and so on. So there is no point starting an auction at $11, you might as well start it at $9.99 and get charged less.
TITLE - Don't try to cram in as much information into the title as you can, because people don't search with words like 'new' or 'rare'. So keep the information down to a minimum, say if it is a CD or 12" etc. and if there is something special like it's 'Japanese' or it's a 'White Label Promo'. You will also reach a much larger audience if you put related band names in the title, so people looking at items listed for those bands will also see your listing.
CONDITION - Giving an accurate description of an item's condition is very import. There are loads of Condition Grading guides on the net for Vinyl and CDs (such as www.musicbaron.com/Vinyl.htm) that go into great detail about exactly what 'Mint' or 'Very Good' condition actually mean. I find the grading of 'Mint' is used far to often on eBay, 'Mint' really means the items appear as new, there are no visible scratches, marks, scuffs (no matter how light) or stains of any kind. If there is any tiny amount of damage then an item should listed as 'Near Mint' or less. In short, be honest. Buyers don't appreciate receiving a CD that was listed as 'Mint', but actually looks like it has been used as a dog toy.
PICTURES - Get a good picture. If the item is of a high value put more than one picture. I like to put a 'gallery' picture on most of my auctions as it can say alot more than words sometimes. Use picture to show the items condition.
COUNTER - You can put a counter on your auctions to see how many people have looked at it. I reckon it helps, if people see that lots of eBay members have looked at your auction it makes it seem more intersting.
PACKING - All I have to say is pack an item the way you would like to receive it. Pack it well, protect it from the world's heavy handed postmen.
SHIPPING - Work out your costs for shipping and put them in your auctions. Show the cost of shipping to everywhere you are willing to ship to and offer insurance as it can cover you and the buyer if something happens to the item in transit.
FEEDBACK - However much information you put into your auctions you will still get people asking questions. You just have to be polite, answer as truthfully as you can and in some cases bite your tongue. Feedback is all important. I value my 100% positive feedback very highly and I value feedback as a means of communicating my experience with another eBay memeber, so when it comes leaving feedback for someone else I like to say it how it really is. If an auction has gone totally pear shaped due to the seller not being truthful about the condition or the item was packed really badly then I believe neutral or negative feedback is necessary, though I always find it hard leaving negative feedback for someone as I know how I would feel about receiving it from someone else. Therefore, I do my utmost to make a transaction go smoothly and to gain customer satisfaction. Don't forget that you can leave a follow up to feedback, which is good if a situation changes after feedback has been left. I'm not saying this is exactly how you should be doing things, just that after alot of experimenting this is what I have found to work well.