1- how to choose quality USB device? 2- how much 1 gb usb will cost me? 3- Do i need to have any special device installed in my pc. (I have USB port) what else i need?
Buy a retail USB drive from a store. I've got a few of them, my favourite is a cheap little U3 Toshiba 2GB stick that I run Portable Apps on. I take it everywhere I go (instead of my laptop). There's a crap load of fake (hacked memory) USB sticks on eBay at the moment - so unless you know what you're buying, stay away from eBay.
Some of the USB Flash Memory devices on the market today are very very slow, especially by writing small files. Read some reviews to find a device with a decent speed. Look for a device that supports the Vista Readyboost function, they should be ok.