Dean McIntyre, the Director of Music Resources in the Center for Worship Resourcing at the United Methodist General Board of Disciple (quite a title!), has written an interesting piece called Fifty Ways to Guarantee Poor Congregational Singing. It is quite a list but boils down to being mindful of your music choices (fits the liturgy, lectionary etc.) with accompaniment that encourages congregational singing.
It is almost impossible not to try and keep score as you read down the list. . . how does your church measure up to McIntyre's suggestion?