What I use to do is.. First downloading the youtube video and then using some software to convert .flv to .mp3 format.
But, one of my friends said that I can directly download any youtube video in mp3 format... but I don't know how..?
Can Anyone help me with this ..?

thanks.

Here is what I normally do to download youtube videos in mp3 format.. (and also if you want, you can download in avi, mpeg, 3gp , mp4 , flv, mov, wav formats).

First.. go to youtube and open the video which you want to download in mp3 format.
Copy the location of the url from the status bar
Next, go to Florinside.com and paste the copied url there in the box
Next, select the output format
and click Download button.

Hope it helped you!