Online discussions also help students understand how to keep a conversation going. Students can't simply answer with "yes" or "sweet" or "lol" as these types of responses do not allow for other students to add to the conversations. Online discussions give students a voice, one that they may not have had in the classroom before. Many students refuse to share their thoughts because they are afraid they will get made fun of or stumble upon their words. By allowing students to take part in online discussion students gain those necessary skills that they can then take with them into face to face conversations. The research has been done, what students learn and use when writing by hand or speaking verbally students take with them into online discussions and what students learns and use when taking part in online discussions gets taken into their face to face or written discussions.
The topics are open-ended as are the guidelines, just get students writing and having conversations with each other and the rest will come into place. If you are starting with younger students, make sure to not spend too much time focusing on spelling and grammar. Over time spelling and grammar will begin to change for the students as they learn how to properly spell words and use punctuation marks but if you spend too much time focusing on that in the begging the students will only worry instead of write.
Be sure to check out my presentation about online discussions in the classroom!