Two "assignments" that help students learn to formulate and write better arguments.  I do these two exercises in succession, but they can be done separately as well.

Have the students think of something they have always wanted to do or have, but someone has prevented them.  You may have to give prompts.  Some students in the past have written to parents for material possessions, spring breaks in Florida, tuition money, more understanding; or to in-laws for acceptance; significant others for help in meeting life goals, etc.  Tell them you the instructor won't see the letter, but a class mate will.  Tell them they should do their best to plead their cases, because a decision will be made based on the letter.  Give the students about 25-30 minutes to write their letters (more depending on your class).

At the end of the time, trade letters between partners.  The partners take on the persona of the letter recipient and then grant or deny the request based on the letter.  This seems to be the hardest part of the assignment for the students.  Hammer into their heads that they must take the assignment seriously in order for it to work.  They then write a brief return letter denying or granting the request and giving all the reasons why.

Students are then asked to answer the following questions:
   Write the answers to the following questions on a separate piece of paper for later class discussion:

1.  Did you accept or deny your partner's request?  Why or why not?

2.  What helped you reach a decision when responding to your partner's request?

3.  What was the most effective part of your partner's argument?

4.  What was the least effective part of your partner's argument?

5.  Did having to respond to an argument give you any insights into how an argument works?  Explain.

6.  What did you have to do in order to create your argument?

7.  Was your request accepted or denied?  Why?

8.  Do you think your partner took the exercise seriously?  Why or why not?

9.  Based on this exercise, what do you think are the ingredients of an effective argument?

 Part 2

    I usually get some excellent papers through this exercise.  Because I allow the students to write about something they care about, the level of passion is high, but I do not allow passion to over ride logic, and this exercise prevents that.

   For homework have the students think of an issue (perhaps narrowed a bit) they believe in strongly and the reasons why they believe the way they do.  They are to list their reasons in some sort of brief outline form.
 

  The second part of this lesson needs a double-session class.  Put the class in their groups (or in groups of 4-5 if you don't have permanent groups), and make sure each group has a timekeeper/chair to run things.  Each person then must state his or her main idea (or thesis or whatever you call it), and give the reasons why.  After that is finished the rest of the group is allowed to attack on the basis of content only, not on moral grounds or you'll be there all day.  Each point should be pulled apart, and the student must do what he or she must to strengthen the argument.  Most student have a very sketchy and "holey" outline when they get to class.  By the time the group is finished, they are usually much more on track.  It is the timekeeper's job to make sure that all members have equal time.

 * Remind students to take notes of what their classmates are saying.

 * Most find they have to narrow their main idea and add a lot of examples to prove their points.

 * Float from group to group and join the discussion, attacking if you need to.  Students usually comment on the fact that I will argue both sides of an issue since many times there will be opposing viewpoints being argued.

   After this class, the students' homework is to write up a draft of an essay based on that day's discussion.  I then go through further group work with my class.  They usually read each other's work aloud, and sometimes I have them bring xerox copies for the entire group, but you can do what ever you like for the writing process.