How can you spot a fake ?

..in clothing or bags? I know how to look for obvious things like designs and quality but what else is there to look out for in telling if something is authentic or bootleg?How can you spot a fake ?
http://www.99sshop.com/ try it, they have many brand products, Such as Nike Shoes,Air Jordan Shoes, Timberland shoes, Prada shoes, Louis Vuitton, Chanel, Coach Bags, Lacoste,Rock%26amp;Republic ClothesI buy from it many times , I am satisfied with the quality , especially for the price .How can you spot a fake ?
omg i am so the one to do this! i am always like looking for imitations and stuff. i kno how to see clothes: jeans, pockets (that's how you tell which brand and if their immitates) shirts, tag and sign in the corner of the shirt (like if you look at the back of the shirt and there's a thick/big tag i can tell which brand it is. and the sign in the left corner of the shirt). for purses you just have to have a good eye.
if it says the brand on it


if it still has a tag


*if it has jewerly then jewerly looks completely fako
Well if you buy a fake designer bag in Chinatown in Manhattan NYC, usually you can spot it because some fakes have the designer's name misspelled just a bit. But that's only for some bags. Also, you can tell because the seaming on the bag can come undone sometimes. Another thing is, most designer purses are pure leather on the inside, and fakes are usually cloth on the inside.