Ways in which I frequently use youtube-dl.

Cheatsheet

List available formats

$ youtube-dl -F URL [URL...]

Extract audio. To keep video, add option -k.

$ youtube-dl -x --audio-format mp3 --audio-quality 320k --embed-thumbnail --restrict-filenames URL [URL...]

Download to different location another/dir

$ youtube-dl -o 'another/dir/%(title)s-%(id)s.%(ext)s'

To extract audio files to a mounted remote file system without uploading the video to such remote file system, you need to download and extract locally, and then move/copy to the remote file system. For example, change current directory to an empty directory, execute youtube-dl storing everything in current directory, and then do something like mv -v *mp3 </path/to/remote/dir>