It is expensive to buy retail technologies like digital cameras and computer hardware in Australia due to import taxes and GST. Set up a paypal account. This is by far the easiest way to purchase on ebay. It can take up to a week to set your account up, but take the time to set it up and your ebay experience will be a piece of cake and will save you time in the future. You are also better protected against fraudulent sellers.
Take your time. Research the item and the seller.
Look at the sellers feedback and look at what other people have bought. If you are buying a memory card for example but most of the seller's other items are headphones and speakers - this will probably not be the cheapest seller you can find. It is better to search for a specialist seller who deals many different brands of memory cards.
Know your product! I'm hearing a lot about fake Sony memory sticks. The problem is, some aren't fake, they're just not compatible. If you buy technology from Hong Kong, theres a good chance even fake memory sticks will work fine, and as my old man used to say, "if it aint broke, don't fix it" so you better do lots of research before fooling around with reformatting and firmware updates. You're taking a mild risk buying a product you've only seen in the picture, so if your unsure don't commit. Paying full retail price from a store will guarantee the product is genuine. But if you're willing to take a small risk you can save a lot of money. I ordered a Sony 1GB Duo Pro memory stick and paid only $7 for it (plus $60 postage) and they retail for well over $100 in the store, and it works fine. I've heard comparisons of the transfer rates differing between fakes and genuines about 10Mbs which the average person will not even notice. If you are dealing with 'duo' sticks, don't assume a 'pro duo' stick will work in your device. Read your user manuals! Impulse buying is easier to resist if you know more about the product. Don't ever bid on an item that is ending within 5 minutes if you haven't been researching it. Watch how much it sells for. Find the item or similar on ebay and find out a "buy it now" or retail price. If you find a cheaper auctioned item, set your maximum bid lower than the "buy it now" price and you will always get a bargain.
Take your time. Be sure to read the entire sellers page! Sometimes a seller will have compulsory postage insurance or high postage so you must factor in these costs. Remember: postal insurance is A GOOD THING, and is worth paying that little bit extra for as long as it does not make your purchase more than retail store prices. Some sellers, particularly technology sellers from Hong Kong will price their items low, but their postage high. This is an attempt to trick the buyer into thinking the item is cheaper, but is merely clever advertising as the price is made up for in postage. However, it is sometimes worth paying a lucrative postage price if your balance is still below "buy it now" or retail prices. A digital camera cost me $80 postage, but i got it for $200 cheaper than it retails here and was delivered in just 4 days to remote Western Australia.
So a Hong Kong seller that advertises the product at $6 but the postage at $60 is not trying to rip you off on postage, they are mearly setting a reserve price to make their bidding price look more apealling. Don't forget that there are a lot of technologies around, so set your maximum bid low early, once, and leave it. If you don't win the item, often you get a second chance offer and this will be based on your last maximum bid. If you keep your max low you will still get a bargain.
Know your product and know your price range - pay too little and its probly a fake; pay too much and could've just gone to your local department store.
Check price is in your countries' currency.
Ensure all postage and insurance are accounted for.
Seller Posts to your location.
Finally, dont be hasty with feedback. Patience grasshopper. Wait until the product is in your hands, which you can't expect to happen overnight (unless you pay for it!) Sellers can usually work out any problems you experience. Negative feedback for problems that could have been easily solved only confuses other ebay buyers. Good luck.