This guide offers great advice on selling items.   I can recommend the following tips:

• The Australia Post 'Postage Calculator' is terrific for giving quotes.  If prior to your auction ending, another ebay user asks you what postage costs are going to be, just advise them to go to the Australia Post Website (Austpost.com.au), and use the Postage Calculator on the left side of the main website.  There they can just enter the weight and postal codes and it will caclulate the postage for you, or if you want to calculate it yourself, its handy to know the site exists, instead of going into the post office every time you need a quote.
• If you are going to sell constantly, a good tip is to buy a small set of accurate scales from 0grams - 2000grams (0-2kg), so you can give accurate prices for postage.  That way you wont have to guess what postage costs will be, and it will save both you and your buyer stress upon having different quotes.
• If possible try not to let the overall packaging of your item exceed over 100 cm in length.  This is because Australia Post will not accept anything in excess of 105cm for occupational health reasons, and thus makes it difficult to give postal quotes, especially if you end up having to hire a private courier company which may cost you a lot more than you expect.
• Own a digital camera.  A good idea if you intend to sell part-time or full-time on ebay and you don't already own a camera, would be to purchase a digital camera.  It doesn't have to be expensive, and you can acquire them very cheaply now so that you can show your item as a picture on your auction.
• ALWAYS take a picture of the item you are selling if possible.  Don't use copied pictures or demo pictures.  There is nothing more that you find sceptical than bidding on an item that says "this item is a demo picture only".  When you bid on an item, you would want to SEE the item you are bidding on, and this will always make buyers more inclined to feel they are not getting "mislead".  Honesty is the best policy, it always works.
• If you want to save time on postage, don't wrap items yourself, just use Australia Post bubble wrap satchels, and or pre-paid satchels, which save a lot of time and hassle for both seller and buyer.
• Try to describe as much about the item as possible, this is a great tip, because when you think about it, if you are going to buy something from someone, the more they describe the item, the safer you feel knowing exactly what you are going to get if you win the item.
• I can't emphasize this more, but be honest and advise as much about your item as possible.  Remember, we are all buyers in one way or another, and the golden rule is do unto others as you would have them do unto you. 

Ebay is a fantastic place to sell and a lot of fun to buy from aswell.  Happy bidding, and I hope your ebay purchases and auctions are a pleasurable experience.