Before you buy
Before you buy an item, find out exactly what you're buying. Just take a couple of minutes to read all the details provided. It might be exactly what you want (and don't be overly cynical otherwise you will miss out on some astonishing bargains), but remember the old saying, "If it looks too good to be true, it probably is". Do a bit of research first, it only takes a couple of minutes using Google. I often go to Amazon, find out the market price, read the customer reviews, then come back onto EBay and buy the item with more confidence. But if you are buying highly technical items, it might be worth visiting dedicated websites for the industry you're interested in.
An interesting point to note is that the picture of the item you're buying might not be a picture of the real item, but just a photo stolen from another website somewhere, particularly from the original manufacturer's website.
Take a look at the seller
If you want more info about an item, go the seller's profile and click “Ask seller a question”. For example, if you spend a lot of money on an item, make sure the seller will insure it for delivery! And is it under guarantee? If so, what are the terms? Check the returns policy too.
Check out the seller himself/herself! What is their feedback rating? How many transactions have they completed? What percentage of positive responses do they have? A 100% positive record for 2 sales isn't very informative! But 99% for, say, 5,000 sales since 2002 really tells you something good! You should be a bit suspicious of sellers who dont have a track record for selling lots of similar items.
EBay and Paypal can help
Find out how EBay and Paypal can protect you. Make sure to complete your transaction on eBay because deals concluded outside EBay are not covered by protection programs. For example, don't pay for an item using Western Union, MoneyGram, etc. These payment methods are unsafe when paying someone you do not know.