Small groups. Make holistic small groups a major component of the regular church life. Have young adults take part in the initial training and lead out in the formation of new groups.
Share a meal and form visitation teams. You could have the young adult Sabbath School class invite all the elders out to a Saturday evening dinner at a restaurant with the purpose of the elders getting acquainted with the young people, and to form teams for visitation.
Retreats. Have spiritual retreats each year for young adults.
Bible Study Training.
Mentoring Spiritual Devotions. Mentor young people in spiritual devotions. Teach them how to build and maintain a successful and vibrant personal devotional life.