How do you actively encourage your congregation to sing?
BIG IDEA: Show how beautiful/awesome/worthy Jesus is.
The call of a worship leader is a tall order. As a broken vessel yourself, you stand in front of your local church, a mix of godly, confused, thriving and discouraged people and try to lead them in something they don't do anywhere else; corporately sing together.
That said, I am often surprised at how often I hear it spoken about as though it is a burden. Many worship leaders speak as though it is their responsibility to prove Jesus is a person worthy of song. This is only partially true. Your job is to point to what is already beautiful and glorious, not make it so. This only works if you yourself are spending time with Jesus, enjoying him. Not just searching the scripture for a song lyric. Not just whizzing over a few verses to lead bible study. Worship him with your heart before you pick up an instrument.
For the burdened worship guy, I have some good news: you're not the mediator. You don't stand between Jesus and the people. You are the people. Enjoy him and sing to him in a way that is mindful of the musical talents and literacy of the room. Sing songs that you're Dad can sing. Balance the celebratory and the contemplative.
Sing things that are true and helpful. Indicate who Jesus is and what he has done, before you expect them to respond. Remind the people of the gospel. We are all forgetful of the great things He has done. Almost no one shows up on Sunday ready to worship in spirit and truth.
Be Prepared
One of those most distracting things in worship is lack of preparation. Keller has said "horizontal sloppiness distracts from vertical worship". Quality matters, but is never a substitute for your need of the Spirit. You can nail the transitions, build the bridge up higher than the ceiling, and weep/sweat uncontrollably, but if the Spirit isn't isn't involved you just participated in an over-produced gym workout. Prepare as though you're about to encounter the king of the universe. Pray as though the Kingdom won't move forward an inch without the 3rd person of the Trinity.
Practice until you can't get it wrong, not until you get it right. Pray for your preparation time, not just Sunday morning. Give space for people to confess sin and remember the gospel before you step on stage. Know your transitions between songs and other liturgical elements.
Teach With Intentionality
Whether it's physical expression or simply singing aloud, it's your job to show/teach/exemplify that corporate worship is biblical, historical, and helpful. Singing with God's people is normative. Use scripture to lovingly encourage your people. Don't be a bully. Don't scold them for not doing something you want them to do...that just means you haven't led them there.
Meet with your lead pastor and discuss what specific area you'd like the congregation to grow in. Plan transitions and song content around that discussion. Ask if your teaching guy would be willing to address corporate worship issues on occasion from the pulpit.
Long Haul
Many of the observations visitors make about our community during worship have been the result of my last 10 years leading people I love and pray for. I've tried things that have failed miserably. There is much I would do differently. But it takes many small victories to see traction in the worship culture of your church. Don't expect a major shift because you spoke for two minutes between songs. It's a long process, and we should be as gracious with our people as God has been with us.