This is an interesting tip.You just need to download and install VLC Player.
Now open any YouTube video.
Select the URL.
Copy that URL.
Open VLC Player > Media > Open Network Stream…
Click Network tab and in the blank space paste the URL and click Play.
The YouTube video will start playing.
Now go to Playback tab.
Scroll down to Speed.
Now You can select Faster,Faster (fine),Normal Speed,Slower (fine),Slower.