Learning to argue academically isn't easy. You should listen to the guidance your tutors give you since the way it is done might vary from subject to subject. Here are some general pointers.
1. Look at the assumptions or things which are taken for granted in the argument - identify those which are weak and discuss and disagree.
2. Support your case - evidence and back up your point of view. Get the resources and data you need and use them effectively.
3. Prove that the argument presented contradicts known facts- find evidence to prove this.
4. Find a hole in the argument- look for a gap in the case being made.
5. Show that the conclusion being presented isn't valid or isn't the only conclusion which could be made - explain why the argument being made isn't strong, believable or true.
