Udisha
The refrigerator test
Real extra virgin olive oil has monounsaturated fats which solidify when cold. If your olive oil remains liquid when refrigerated, it is most like a low quality blend.
Harvest date
Always look for the "harvest" on a bottle of extra virgin olive oil which specifies the time the olives were picked. A cheaper, inauthentic version will only contain the expiry date.
The taste of pepper
If your olive oil is real, it will leave a peppery taste at the back of the throat when swallowed. However, if you taste nothing it is definitely diluted.
Dark glass
Light is a major enemy of olive oil, it brings down the quality. Real extra virgin olive oil will always come in dark glass bottles or tin cans. If the oil comes in transparent bottles, it is not the real deal.