Oh my. Heh. That brings back some memories.
You're 19 and head of the Youth Dept?! Is there no Youth Minister?
First- Chaperones. Legally you're an adult, but you'll need some "real" adults as chaperones, preferably a couple of parents of some of the youth.
Second- Agenda. Have a general theme along with a format. Stick to it as best as possible.
Third- Pick a place where the boys and girls can easily and fairly completely be watched and seperated, specifically if it's also a "sleep-in".
You and/or the Youth Minister can pick pretty much any topic as a theme, though certainly it should be relevant to the teens and youth. Along with this, plan for entertainment, recreation, refreshments, whole group time, potentially small group time and individual quiet time.
Have everything planned out, along with extra things to do - just in case, and above all, be flexible. Take the time necessary to get proper approval, funding, materials, sites, etc. Also, give your youth several weeks advanced notice.
As a youth I went to lock-ins at people's homes, in our church, other churches, and state Baptist facilities. Some were for one night, some basically a weekend retreat. Some of the over-night lock-ins were event packed all night, no sleeping, and some were sleep-ins. We'd watch Christian or secular movies, relevant and not. We'd play various kinds of games, some indoors and others outside. Some places provided a cafeteria, some just snacks and sometimes members of the congregation would cook and/or bring food for us.
I don't recall any of the topics, but to be sure we had mini services and Bible studies along with some quiet times for reflection.
If you have no Youth Minister, I'd bring this up to the Pastor and perhaps some of the deacons and even some of the parents.
