like the outside and the software and the themes they haves i mean if it has a camera it like 1.3 or the other one a 2.0?? do they have different themes but mostly the outside i mean come on look at the iphones rip off they look way different outside of them and they will have it spell nokia differently and the phone might be smaller or bigger denpending on the phone

the fake ones never really have nokia spelt correctly usually its nokya nocia n so on
the make of the phone is different it will have a slightly larger or smaller screen key pad ect

there is one easy way:
first press *#06# and find out the imei number after that call nokia helpline and ask them weather it is orignal or fake… simple..

the price is the most important way,there are many people buy the mobile in discount time in China,if the mobile is much cheaper than the same types,it must be fake,in my opinion Nokia is very good to use,it can use more than 2 years.also in China have a very famous web site store ,it’s name is taobao ,many Chinse people buy anything thought the net,also you can get the very good mobile though the net ,i am the taobao agent ,i can help you!
I am a local chinese buy agent, i can do purchase for foreigners with chinese items to help their small business or daily life use,things could be from taobao.com and other china online shopping sites or china wholesale market or directly from factories.www.taobao.com is the biggest C2C online shopping site in aisa,it is just like another ebay,you can find cheap brand cloths,shoes,bags there,some are the order rest from china OEM factory,and some are 1:1 highly alike replica. If you are interest in this area,can add my msn messager:wxcansen@hotmail.com for further chatting.
Hope it helps!