PLEASE help, i want to select none for my payment method on my apple ID...?

[infinity on high]

so yea, for the payment method on my apple ID, i want to put none, mainly because i just want some free apps for my iphone, i wont buy anything atm. how do i do this? when i go on itunes store, it says i have to review my apple ID, so i do, and then the payment methods come up, with no option of 'none', how did everybody else do this?
PLEASE i really need ur help, and thanks!!