Firefox's "DownloadHelper" works GREAT! Not only for youtube, but for virtually all embedded video/audio!
no worry be happy. its easy as 123. the best way is to install the world # 1 internet download manager. it increase download speed up to 5 times. www.internetdownloadmanager.com here u can buy world's best price IDM serial number for life time validity from IDM's authorized reseller http://www.systemicsoft.com/downloadmanager.html USD 17.00
I just use Internet Download manager to download video from you tube. Just click on the video and then will automatically downloaded.
I use youtube downloader. It's fast and easy and it has an additional feature which is the converter.