How can I save Youtube video?

What do you want to download them as? Video (with audio obviously) or just audio?

look here

http://ubuntuforums.org/showthread.php?t=547848

That may not work anymore sorry - It depends on which version of flash you have. Try here

http://ubuntuforums.org/showthread.php?t=1714940

There are also a number of add-ons for Firefox that let you do this

Saw both both links. I can see several items in them. Among 1714940 which one would you prefer?

Which format do you wat to download from YouTube in? You failed to answer my very simple question. Do you want the video or just the audio.....

I am very sorry, Actionparsnip. I must mention it in my first question itself. I didn't notice that one line answer. Then I didn't expect 3 answers just before this message box (in which I am typing). .......... I meant downloading videos. No problem with audios.

I recommend the firefox extension "unplug". It is actively maintained.

I had already installed video-downloadhelper. I had mentioned in the question itself ( as Downloadhelper ). But I don't know how to download.
I didn't understand "unplug" & 'youtube-dl' in the repos.
As I have already installed video-downloadhelper I shall try it first.

Need I change the Preference/behaviour/extended download menu of Video downloadhelper? or add anything in Preference/capture (of the same)?

unplug is a firefox extension:
https://addons.mozilla.org/en-US/firefox/addon/unplug/

I downloaded unplug. But not working well. So I used Video-downloadhelper. It is working well. Thank you mycae. I will try unplug once again if there is any problem.
Thank you Actionparsnip. Your suggestion helped me to try it again.

Thanks actionparsnip, that solved my question.