I would seriously forget about the first link RadDave posted, unless you have a working knowledge of Terminal. If you download the LionDisk Maker that Harry posted, and have the "Install Mavericks" installer already downloaded onto your Mac, then go that way, as it steps you through the process and is very easy to use.
Just FYI, when using either way, let the LionDisk Maker or Terminal do its job and finish before you eject the USB. I say this, because both ways, you will feel as if it is doing nothing, (as there is no bells and whistles or loading indicators to let you know the progress of the job being done).
Leave it if you are unsure, or if you really need to know if its working, right click or ⌃+click on the USB and get info, and look at the size of the USB. If you do this a few times, you will see the size increase, and it should increase up to about 5.7gb all up.