Get into the habit of checking a seller's feedback BEFORE you place a bid. From the feedback table you can find out if the seller has had any negative comments and decide if you want to trade with the seller. Generally, ebayers are genuine folk who are honest and helpful but please be aware that not everyone operates in this way.
Getting your money back via paypal is a lengthy process if something does go wrong but better than if you send money by any other means such as postal order/cheque or cash.
Please remember to check the seller out before you press that bid button folks!