FIRST, do some freewriting; reflecting on your chosen text, write without stopping to correct or read your writing. Write down any ideas that come into your head about the text. Dont worry if they are dumb or smartall ideas in a freewrite are good ideas. You can mine the sentences for gold later! As you write, consider these ideas to get you going.

How does the text make you feel? Why?
Do you agree with it? Why or why not?
Does it successfully convey its message? Why or why not?
What (if any) personal experiences help you relate to the text? 
NEXT, mine the freewrite and tell us:

What were the three best ideas that came from this exercise? Note: this response should be focused on the ideas as they relate to your chosen readings (not on the idea of freewriting itself).
What will your thesis statement be (you will have a chance to work/revise this next week)? To review thesis statement creation, click here: THESIS STATEMENTS
In your textbook reading, Chapter 2 defines a thesis as a statement that identifies your topic and your opinion about that topic. As we are in the planning and drafting stages of writing for the essay, its important to think of your thesis statement as fluid. This means your thesis can, and likely will, change as your ideas become more developed and concrete. Right now, you do not need to think of your thesis statement as something solid and set in stone.

For the Reader Response Essay, your thesis statement should accomplish the following:

Focus on one of the texts provided (Mother Tongue or The Crane Wife).
Clearly capture your response to the text and why you are responding that way.
Provide a position that expresses what you think about the essay you read.
Remember that a strong thesis statement:

is a single sentence (the last sentence of your introduction)
is a statement, not a question
is in the present tense, not the future or past tense
meets the 4 Cs (clear, concise, comprehensive, and makes a claim)
in order for a thesis statement to make a claim, it must push beyond summary and into analysis (not just what happens in the text, but why you responding in the manner you did).
You can find an example of a thesis statement for a Reader Response essay in the student sample essayPreview the document. In this essay, the writers thesis is located at the end of the introductory paragraph. It states:

Although Adrian was ambivalent about his dragon tattoo, his article provides a convincing argument for getting tattooed.

Note that this thesis statement notes the writers main response to the article.  In this case, it sets readers expectations that Adrian (the last name of the articles author) provides a convincing argument for getting tattooed.  This thesis, therefore, offers a positive response to the article.  Readers will expect to read the rest of the essay to uncover just how or why the argument was convincing.  In a Reader Response essay, your thesis can be positive, negative, or a combination of both.  The key element is to ensure it makes some claim about the effectiveness, importance, or impact of the reading you have chosen for your response.