I just don't want to be too long, so lets get straight to the work ;)
1) A small application called UNetbootin which you can download from here.
2) USB drive.
3) Ubuntu ISO, if you dont have ubuntu iso download one from here.
Step #1: plug-in your USB drive and make a back up of it because your drive will be formatted in this procedure.
Step #2: Launch UNetbootin by double clicking it.
Step #3: Now select "Diskimage" and browse to the ubuntu iso and select it.
Step #4: Make sure that the "Type" is selected as "USB drive" and also make sure that the drive letter belongs to your USB drive.
Step #5: Now click "OK" and pay some patience till the procedure is completed.
Once the procedure is completed click "EXIT", from now you can install or enjoy live cd right from your USB drive.
Here is a video tutorial by which you can do more easily.