How should i install Fedora onto flash drive .. to boot the OS from flash drive..
plz help me in that!! 
From an installer CD? Treat the flash drive as just another hard drive.
from installer cd..do i have to install any plug-in into USB..
so that USB gets detected at booting time?
---------- Post updated at 03:05 PM ---------- Previous update was at 02:27 PM ----------
Install Fedora from Windows
Run the wizard - Once you have your Fedora ISO and have copied and installed the Fedora Live USB Creator, run the program and you'll see this.
Select your ISO - If you already downloaded your Live CD, click Browse and choose it in the file selector. If you want to download Fedora now, just choose your version - note that only Fedora 9 and above support persistent storage.
Allocate space - Unless you have a tiny USB stick, drag the Persistent Storage slider all the way to the right to allocate 2GB for your documents and settings.
Sit back and wait - Now sit back and wait while the Live image is unpacked to your USB stick and the overlay storage is created. This should take no more than 10 minutes.
Bootloader installed - Once it has finished configuring the bootloader, the Live USB Creator prints a simple "Complete!" message and you're done - now close the window.
Ignore the errors - In each of our tests, we received a message about there being errors during the installation, and yet everything was fine. Just click on OK to skip this message.
---------- Post updated at 03:05 PM ---------- Previous update was at 03:05 PM ----------
shud i follow this??
Yes, use Fedora LiveUSB Creator.
If you want to try other distro go to this site. Boot and run Linux from a USB flash memory stick | USB Pen Drive Linux