If your group is small, go in with other groups on things. Pool your resources. Don't be afraid to invite another youth group to some of your activities, even if they are of another denomination. Don't expect them to go away on their own. If you have ten young people who will call ten other kids, you can personally contact a hundred kids in one evening.
Personal contact is always the most effective.
If your church does not have a good youth resource library, then start one. It should grow every month. Include books for kids, their parents, and your leaders. It's easier to enlist those adults when they know they have been chosen by the kids. Most schools need help for the lunchroom, dances, assemblies, field trips, or sports events.