1. Don't interrupt others. Give them an opportunity to put across their point. Patiently listen to them, you never know it might help you in your discussion. After all your aim is to conduct a healthy discussion. If you're interrupted, nicely request to be allowed to finish.
2. Don't get into arguments with anyone. If there's one going on already, try to resolve it so the whole group can move on.
3. Don't go off topic. Bring the group back if they are going off topic.
4. Lastly keep your self-updated with the latest happening in the market.