You don't need to download a local version. Just run
This will check for the latest version and install it. This last part is optional but you can run
youtube-dl --version before and after the install to verify if it updated successfully.
Also, in very rare occasions sometimes the latest update will not worked. You see, google doesn't want anyone downloading the videos and they're always changing things around. Which is why you need to run
youtude-dl -U very often.
Here's a tip for better file name titles.
Add
-o "%(title)s.mp4" or
-o "%(title)s.flv" after the link to get better titles for the videos.
For example
youtube-dl -f18 <youtube link> -o "%(title)s.mp4"
or
youtube-dl <youtube link> -o "%(title)s.flv"