That is a big general question.
First thing you need to do is become familiar with the base techniques of figuring out the different kinds of conclusions and premises, and the assumptions. Once you are comfortable with those, it is time to move on to the question types. Learn to differentiate the different question types as they ask you to do very different things. There are over 9 of them and each has its own little technique as well as traps to avoid and useless information to filter out.
Learn one question type at a time, practice on such questions then move on. Once you have them under your belt start practicing on all question types so that you get used to knowing how to tell them apart. Always remember your base of figuring out your conclusion, premises, and assumptions and apply the knowledge to what the question is asking you to do. This may seem obvious, but for many it is not. Don't be afraid to take notes as well as this helps you focus and organize your thoughts.
What I have given you are very general guidelines. You will now have to start looking for information on the techniques (which is a bit too big a topic to include here obviously!)- remember: Start with learning how to break down the argument properly; without this, not much improvement and success will take place.