1) Add 'kiss' in front of any youtube link to download the video.
For example:
youtube link: http://www.youtube.com/watch?v=aW3e7rlumDA
change it to: http://www.kissyoutube.com/watch?v=aW3e7rlumDA
2) Click the down arrow button for normal version or 'HQ' for high quality version of the video.
The video will be in .flv (normal quality) or .mp4 (high quality) format. If you can't play the videos, refer to this guide.
If you encounter slow download speed, check out the Social Media Grabber instead, it splits a file into several parts and download them simultaneously so it downloads much faster :)
Alternative way
You can also visit http://www.tubekeeper.com which can download Youtube / facebook / metacafe / dailymotion video in just one click.