To fully use its features you should install ffmpeg though. Youtube-dl will automatically use it if it's in the PATH, and then can download Youtube videos with higher frame rates and resolutions (they store video and audio in separate files, and ffmpeg is used to mux both together). ffmpeg is also required to download from some streaming video hosters.
For me it's essentially:
youtube-dl -F '<url>'
to get the list of available video and audio formats, followed by youtube-dl -f <video format>+<audio format> '<url>'
and then wait for the download to complete. And youtube-dl -U
to self-update youtube-dl (because it gets updated just about every day).