hashtagging on youtube

Immediately after description we can give hashtags. My question is how many hashtags one should give. Also what care one should take while giving hashtags where the description ends?

I'm new to this youtube community, and getting myself out there in the world besides my close group of friends. What are some good hashtags that you can use on twitter, instagram, facebook, etc

Hey guys, recently I've been using quite a bit of hashtags on my youtube videos and I've noticed form "TubeBuddy" which is like a analytical toolkit to help you with stuff like what people are searching up, how many people, and if the ratio between them is good. It also has a lot of other...