Secondly, check to see if the product comes with an instruction manual, especially for watches and mp3 players.
Thirdly, look at description to see if batteries are included, if they aren't check for battery size.
If buying more expensive electronics, like a fake iPad (£80). Check delivery method. It is recommended you have postage insurance and/or a tracking number for your product.
Fakes and clones aren't always rubbish. I have an mp3 player which looks just like a 2nd generation iPod Shuffle, it was £5 and works perfectly.
FINALLY, make sure you ask the seller any questions BEFORE you buy, because - A: You don't want to buy something you didn't intend to and B: Most China sellers can't write good English.