• Discard offers from sources that ask you to pay fees, taxes or other charges to clain a prize.  No legitimate company would ever do that.

• If selling something, say through eBay, never accept more than the sale price.

• If accepting payment by check, ask for one drawn on a local bank or on a bank with a local branch.  That lets you personally verify the check's validity.

• And remember, if something seem too good to be true, most likely it is.