I believe that public forum was designed to have a "john or sally doe" off the street come in and be a judge.  That means that speaking clearly is absolutely essential.  If I cannot understand you, I cannot weigh what you say.  I also believe that clarity is important.  Finally, I am a firm believer in decorum, that is, showing respect to your opponent.  In this age of political polarization and uncompromising politics, I believe listening to your opponent and showing a willingness to give credence to your opponents arguments is one of the best lessons of public forum debate.