Which Air Cooler Should i Buy?

I want to buy a new Air Cooler. For this I have seen various kinds of Air Cooler and it’s seems to me that all Air Cooler are good But I know all are not good. For this it’s very hard to choose perfect Air Cooler for me because I don’t know and understand anything about electronic product even in Air Cooler. But I want to buy a good Air Cooler. So I want help from the expert person.
My questions is –
What should I see before buying a new Air Cooler?
I will be very grateful to you if you help me to buy a good Air Cooler.
Thanks to all