If you can, don't use a reserve. Put a starting price of what you need to get for the item. People will either buy or not regardless of price.
Don't start your auctions at a price that you can't afford. You will lose money that way.
Keep your shipping to a minimum. People get crazy about shipping amounts. If you charge a handling or packing fee, make sure that is in your auction.
No, that is not true. The item is not worth "what you need to get for" it. It is worth what a seller will pay. Otherwise keep it and save yourself the fees for a failed sales attempt. The best policy is to advertise it properly and list it long enough for the marketplace to decide what it is worth. You can always take it to a dealer and receive what it is really worth to someone else who has to make a living selling what you don't want anymore.