What phrases can I use to structure my arguments and express my opinions?

In a conversation or essay you need to have some phrases to show what your opinion is and whether you are in favour of or against the argument you are debating. 'Ich denke, dass' is good, but it can get a bit boring! Try phrases such as 'meiner Meinung nach' or 'ich bin der Meinung, dass' to explain your opinion.
Phrases to show whether you agree or disagree are also important - phrases like 'ich stimme zu' or 'ich bin einverstanden mit' can help you agree, and to disagree phrases such as 'Ich fürchte, ich muss Ihnen widersprechen', 'das ist nicht immer der Fall' or negating an agreeing phrase.
There are of course lots of other phrases! It's useful making a list and learning them until they come naturally. Let's practice a conversation now though and see how many you can fit in.