Youtube is very liberal when it comes to their keyword video tags. Here's an actual statement from there self help area: "Enter as many tags as you'd like into the tags field" They also state that individual tags can be up to 120 characters in length.
A good suggestion would be to use about 15 tags when you start converting your newspaper on line articles to video. Just make sure to only include video tags that are related to your video.
Lets say you have some articles about online business marketing listed in business newspapers that you want to create article videos for. Some good keyword video tags you could use might be, "online business marketing","How to marketing a...
