Invite-Don't Pressure. Solicitation of people to participate in your group may result in their feeling pressured, especially if you have a supervisory role. Some employees may feel that their jobs are in jeopardy if they don't attend.
Be Professional. Prayer before a business meeting, even in companies with roots in Christianity, may be viewed as unprofessional and may jeopardize any good feelings non-Christian coworkers might have toward Christianity. Be sure that open prayer is acceptable in that corporate culture and that all parties involved desire open prayer.
Voluntary versus Mandatory. Some over-zealous managers have attached prayer sessions to mandatory meetings. This can easily backfire and make you legally liable.
Avoid Christian Lingo-So often we forget what life was like before we were Christians. We often use terms like sanctification, born again, Spirit-filled, etc. The non-Christian will quickly get lost in that language. If you want to be understood by the non-Christians in your group, you must avoid religious jargon.