Step 1: Run Opera min from your phone and type m.youtube.com
Step 2: Find and select the video which one you want to download.

Step 3: Now have look on the address bar. Its showing something like this m.youtube.com/watch?......
Step 4: Just put ss instead of m. like ssyoutube.com/watch?...... and press go.
Step 5: You will see some video format list. Select in which format you want to download this video. Enjoy YouTube videos on the go..

Hope you like this trick. Please don't forget to share it..