It couldn’t get much simpler, even if YouTube added their own download button. Replace the “Y” of any YouTube video URL with a “3” and you’ll be automatically directed to 3ouTube’s awesome download service which allows you to download the video with a click or two.
For example, say the URL of the video is http://www.youtube.com/watch?v=tgbNymZ7vqY (one of my personal favorites). All you do is replace the “Y” in YouTube like this — http://www.3outube.com/watch?v=tgbNymZ7vqY (bold added by me). Voila.