As stated in the subject, I need to know the best way to differentiate between a knockoff designer item, and a genuine item. Specifically, I have a Chanel handbag that may or may not be real. How do I tell?
(Mods, if this is the wrong category, please move.)
Labels. Obviously. 
Apart from that look inside at the lining, the quality of the stitching, the seams, generally the finishing.
If it’s genuine all of the minor things that aren’t visible from the outside will be as well made as the things you can see.
since i’m a guy I can only speak about men’s clothing.
Designer brands have seriously superior materials to knock offs.
if it feels like crap, it isn’t a real designer label.
Look yours over very carefully. Then go to a store that sells the real thing, and check it out. If there is no apparent difference, you might have the real thing. I say “might,” because some counterfeits are actually made in the same shop as the real items, after hours. In other cases, Disney and Tommy Gofigger sweatshirts will be faked embroidery on Hanes shirts, with Hanes labels.
While you are probably correct about the “after hours” thing, I had not heard it before. Can you cite an article about that. I’d like to read.
For Louis Vuitton bags, if the stitching in the handle comes apart after a couple of months, it’s genuine. (Sorry, my wife had a bad experience with them last year. She’s still addicted to LV, though).
Seriously, though, if you go to store with its own Chanel section and tell them your concerns, they could probably check it out for you. I’m sure someone who sells or repairs Chanel for a living would recognize the differences in quality pretty quickly.
Price is sometimes a good indication. Some people may not know what they have, but a lable listing it as a Chanel would be a big clue.
Now that E-bay is so popular, people know the value of stuff more:
“neat, Aunt Martha gave me this bag. I wonder what I could sell it for?”
They aren’t going to sell it for 5.00 when they see them selling for 200.00.
This is more true if a stranger sells it to you. Why would they want to sell it for cheap when they can sell it for more on E-bay? That is, unless it is stolen merchendise or a fake.
The above may sound logical, but apparently not all people feel this way. A co-worker once came in with a new LV purse. She got it for 25 bucks at a flea market form a lady who ‘didn’t know better’! She couldn’t believe what a bargain she had snagged. A real LV purse! WOW!
…didn’t know how to break it to her that Vuitton has 2 t’s…
wal mart and Goody’s both counterfeited Tommy hilfinger so it will be hard to tell if something is genuine
Well, I can’t find any case histories, though I did find a couple of articles referencing this phenomenon:
OECD Report, The Economic Impact of Counterfeiting (PDF, p. 12):
I also found an interview (in PDF, again) with someone who chases after counterfeiters. I can’t vouch for the accuracy of what’s said in it, though.
And just for grins, this is the U.S. Dept. of Justice’s definition for “counterfeit marks.”
A related phenomenon (and another term you can use if you wanted to do your own search) is “parallel trade.”