Quality of accessories.
A brand always checks the accessories and make sure
that the accessories are good in quality and defect free before
forwarding it for an open market.
A brand is always aware of the packaging of its
product, a fake product will not have a good packaging and you will
definitely find some faults.
The brand always makes a product's manual according
to the customer, and if you are receiving a manual in a non-local or
any other language (except English), then the chances are it is
A brand's logo is the best way to figure out if the product is fake or not.
In a fake product, the logo will have a slight change, which will look like the original but will not be the same time.
Every country has their own standard accessories
like a charger, if you don't find the charger according to your standard
electric plug then it might be a smuggled product.
Also, the brand doesn't use two-tone colours in their chargers.
If you find the plastic in two different plastic shades then it might be a fake product made with a cheap plastic.
Wires and plugins.
Fake products don't have much detailing.