TruthMedia has a nice article from the TruthMedia Internet Ministry Training Centre - How to Minister on the Web. Their context has to do mostly with chatrooms and emails, but the same applies to any online interaction. They remind us to make sure you have a Christ-like attitude as you interact. For example, one should:

• Show compassion
• Lead people Jesus
• Help visitors understand a Biblical world-view
• Trains people to walk in the Spirit
• Encourage them to be involved in community