Well, I'd say take content you yourself like. Maybe something with value. It's always nice if people who are passionate about something are involved.
Regarding websites: I'm not sure if that's the correct way. Usually they're done by a small closed group. And if you want to be a pirate, you have to climb the ladders. There isn't a simple tutorial that makes you the captain stright away. You start scrubbing the deck, learn how things work, gain knowledge and choose where to get involved. Slowly you'll learn and someday may be crew or even first mate.
So dive in. Watch. See what you like and see if there's something at that place that could need your attention. And ask the people there.