Both you and your partner should take an equal part in the discussion. Make sure you give your partner a chance to speak.
Remember that you don’t have to agree with your partner’s opinions, but you should reach a decision together.
Before the exam, learn and practise phrases for giving your opinion, asking for your partner’s opinion, and agreeing/disagreeing, for example “As I see it,” “From my point of view,” “I believe…” Practice with them so they sound natural.
If you don’t know anything about a topic in the Speaking paper, do not speak about something else!
You need to show your language skills, not your knowledge about a specific subject.
Again, use expressions to react, but they should sound natural. You can use expressions like: “I completely agree with you.” “I’m not sure we see eye to eye on this point.” “That’s a great point.”