None. I just mumble very softly; hoping to avoid difficult octave changes, hoping nobody hears me, and hoping nobody notices that I’m just mumbling and waiting for the song to end, so I can sit down and read my bulletin.
See, this is the problem with church music nowadays. Either it's three-chord happy clappy stuff with banal lyrics on an overhead projector, or it's the same old dreary hymns sung half-hearted and out of tune to the accompaniment of a dusty old organ.
There is a remedy for this, and that's to revive the Sacred Harp tradition of a hundred and fifty years ago. Also known as shape-note or "fasola" style, it's perfect for people with no formal choral training who nonetheless like to belt out hymns of real substance and depth. Search YouTube for "sacred harp" and hear robust, rough-hewn songs of deep and trusting faith sung the way our remote ancestors sang them.