Pack but do not seal your items before you list the item. This serves two purposes; first you can check the exact cost of shipping, either by the mail service or courier. This means you can set a fair shipping cost in your listing. If you charge it too much above the actual cost the buyer might complain and reflect this in their feedback, charge too little and you will lose money.

Know all of your costs.
There is more to the cost of shipping than just the postal of courier charges. Have you had to spend money on packaging materials? It would not be unreasonable to ad £1 to an item to cover the cost of packing materials. Does it cost you anything to take your packages to the post office or the distribution centre. Are there any insurance costs that need to be paid and if so who will pay them, you or the buyer?

Communicate
Once the auction or sale is over it is a good idea to email the buyer and congratulate them on their purchase. In the email you can also tell them when you expect to dispatch the item and suggest that if they do not receive it within a certain time to contact you. You can then promptly chase it up with the shipper.

Get it away
The quicker you can dispatch the item the faster it will get to the buyer. Nothing impresses buyers more than a fast delivery. It is one of the most commented upon facts in positive feedbacks.

Look at all the options
The majority of sellers rely on one shipper whether it is the mail service or a specific courier such as Fedex or UPL. For small items normal mail may well be the best option but for bigger items or if you are selling large quantities on a regular basis it could be worth shopping around for quotes from all available shippers.

They say that the opera is not over till the fat lady sings, on eBay the sale is not over until the customer gets their goods.