Having bought and sold for many years on ebay, I have learned that you really need to check the seller's feedback - it speaks volumes about the seller.
Bypass any newbie sellers - only sometimes will you get a good, honest deal from them.
A seller can have good feedback, but if they do not have any recent feedback, I would hesitate buying from them. Dormant accounts are hijacked everyday on ebay, and the scammers use them to sell expensive items.
READ the description well - note the grammar and spelling also - those who are honestly making a living through ebay, will use spellcheckers and have correct grammar.
ASK any questions before the auction ends. No response from them - a big red flag not to buy from them.
Use paypal for sure - for a buyer that is your guarantee that you will at least get your purchase price back if the item is a scam. Avoid the auctions who only accept money orders - you have no recourse as a buyer if they are a scam. A money order is as good as cash, and you know not to do that through the mail.
And the big one - If it seems too good to be true, then it probably is a scam. I have gotten a few good deals on ebay over the years, but for the last couple of years they have been almost non-existant. Buyers are more savvy and the really good deals don't happen too often.
Be careful and good luck!