Public praying is a responsibility as well as a privilege... Many facets of Christian discipleship, not least prayer, are rather more effectively passed on by modeling than by formal teaching. Good praying is more easily caught than taught. If it is right to say that we should choose models from whom we can learn, then the obverse truth is that we ourselves become responsible to become models for others. So whether you are leading a service or family prayers, whether you are praying in a small-group Bible study or at a convention, work at your public prayers.
-- D.A. Carson, A Call to Spiritual Reformation (page 35)
And just to head off potential objections... before you suggest that it's always a sin to give thought to the way others will hear your prayer (as in Matthew 6:5-8), take time to wrestle with Jesus' example in John 11:41-42.