I follow a very simple, and quite catchy, rhyme when it comes to training my youth group girls to do ministry:
Do what you do, just add one or two. It was originally suggested to me by a friend at church and has stuck in my mind ever since as I think about what I am doing at church, and more importantly, who am I doing it with.
When it is appropriate, I always try and involve another person in whatever I am doing. It doesn't matter if I am simply shopping for supper or meeting up and reading the Bible with another person. Whenever I am doing ministry, it is an opportunity for me to be showing another person how I serve, and it is an opportunity for them to observe and learn.
If I sign up to the church cleaning roster, there is no reason why I can't invite others to serve with me. If I am asked to provide supper, there is no reason why I can't bring another person to the store to buy food. If I am looking for opportunities to speak with new people at church and make them feel welcome, then why wouldn't I want to include another person and do it with them?
This also impacts how I choose which extra things I say yes to in a busy week when I am already up to my eyeballs in ministry. Can I use this as an opportunity to teach someone else? If the answer is yes, then I am more likely to say yes. I have said yes to helping at friend's church's play groups and holiday kids' clubs in order to give others at my church a chance to join me and serve in this way.
Inviting others to join in when you are serving is the best way to teach them to serve. How do I know this? Because this is how I was taught.
For my first three years at youth group, I lead a Bible study with an older, more experienced girl. By watching how she interacted with the girls, by chatting and praying with her, I learned how to teach Bible studies and connect with my youth group girls. Whenever my church went out and did walk-up evangelism, I was with someone more experienced. My previous Bible study leader constantly involved me in her life, and I had the chance to serve beside her plenty of times. I was rarely just thrown in the deep end. I had the chance to learn from her what ministry and serving Jesus looked like.
So do what you do, just add one or two and do ministry together.