How do I write an essay comparing "Boys and Girls" and "Mirror Image" by Canadian authors on the topic of dreams vs. reality? I want to compare...

First of all, you will need to find a common thread
between the two stories.  For example, you might say that both of them demonstrate the
conflict between dreams and reality, or the loss of hope.  Then, you describe how the
authors use characterization, mood and symbolism to explore the theme in each
story. 

Once you have your thesis, I would choose to write
a paragraph for each of the elements you listed.  For example, your first main point
paragraph would be about how the author uses characterization to explore the concept of
__________________ (whatever your thesis is related to dreams and reality).  For
example, you might say that one character is hopeful and another is pessimistic. 
Explore their character traits, and how the authors use those traits to explore the
theme.

Then, your second paragraph would do the same thing
with mood.  How does the atmosphere of the two stories compare?  How does the atmosphere
relate to dreams?  Is one story more realistic to
you?

Finally, choose important symbols from both stories
that mean the same thing or something related.  It might even be the same or a similar
symbol.  Explore how the author uses it to relate to your thesis statement about reality
and dreams.