One of the most important things to remember is add postage and payment methods at the bottom of the ad, so many people miss this out.
Customers want simplicity, no music, no funny animations.
Especially when you start off make sure the minimum price is a price you can afford to sell it at, if you are selling multiples of the same item you can always try an auction starting at a low price to see what happens, you might make a big profit or a huge loss.
If you have terms and conditions make them very short and sweet, otherwise you will put customers off.
Paypal is a must for sellers you will lose a lot of business if you don’t allow them this option.
Make sure your postage and packaging is reasonable.
Have a look in the ebay advanced search, completed items for similar products to your to see what price they reached, use their ad as a basis but don’t copy or steal their photos, it is both unethical and ebay do not allow it.