Giving the characters a reason to act together will be help to get things going, I would say. Otherwise you run the risk of the players going off in a dozen different directions, with or without plots of their own.
Giving links to other characters helps as well, as it gives them a reason to act together.
If anyone wants to link my PC into their own background, assuming my character draft gets approved, he's a wandering Fangshi (exorcist), dealing with restless spirits, supernatural threats and wandering monsters. He could have been hired by an authority figure to deal with a particular threat, or met other wandering characters on the road.