Being a leader of young adult ministries, I have come to a few conclusions concerning this matter.
1. Make sure you are not preaching to them. Get everyone involved in the discusion. Young adults really like to give their opinions on things, especially when it comes to their faith. If you are a leader, mediator, whatever, group discusions and not sermons seem to be the key.
2. Make sure that the church is aware of the problem concerning young adults attendance at church and need for this ministry. Churches around the country, have had a steady decline in attendance of people 18-29. Almost a 48% decline. Also most of them are not being recognized as the new leaders of the church, or body of Christ.
3. Make the classes, study, etc... as exciting and to the point as possible. In my experience, young adults seem to have the attention span of a spider monkey. (being 28 myself I know this first hand)
4. Let them know that they are wanted inthe church. I know there are the people that will look at you and ask "Oh havent seen you for a while, I thought the roof was going to fall in when you showed up" Some people just don't see the hurt in there comments. You have to be the person that steps up and lets them know that you have been praying for them and make them feel accepted no matter what their background is.
5. Following the points made in 4. Really make an effort to know these people. Try to plan a couple activities that will be fun for everyone. We try to do theme parties. (I.E. an 80's party, beach party, etc...) You have to plan pretty far in advance for these type of things, as young adults usually have a pretty busy schedule.
Well I hope that either helped you in your mission, or you got a good nap after readin this. God bless you in this ministry, and don't give up on them.