1. You start by having half of the affirmative speakers get up in turn and present one single argument (no more than 30 seconds each). Everyone is instructed to write down and number each point, so if there are ten affirmative speakers in the first point, they should have numbered arguments one through ten in the first column of their notes.
2. Before the affirmatives start, let the first negatives know that they will be responsible for refuting one of the affirmative arguments (have the speakers numbered in a sequence so that if a person is negative #2, then they know they refute the 2nd affirmative argument. Once the first group of affirmative speakers have finished, have the first group of negative speakers answer each of the affirmative points.
3. Following this, the second group of affirmative speakers are up. Their goal is to defend one of the original affirmative arguments by attacking the negative response to that argument.
Again, each person has a number, so affirmative #3 would be expected to defend the 3rd affirmative argument by attacking what the negative says against that argument.
4. Finally, the second group of negative completes the process in the same manner. If you like, you can add judges who present a decision.
5. The goal is to have an informal free-flowing exchange and to keep things moving so that everyone speaks. Even if the arguments arent very good, we will get the idea of structure and given the numbers you should hear at least a couple of good arguments and good answers.