Here are some tips for submitting your CA application:
CS106A, 106B, and 106X: These are extremely competitive positions. The department hires one Head CA for each of these courses. The position almost always go to someone who took CS106 at Stanford and served as an undergraduate Section Leader for several quarters. If you were not a CS106 Section Leader at Stanford, chances are very slim you will receive one of these positions.
Use the Qualifications Field to make your best case: This is the field where you should describe your knowledge of the material and your teaching experience. This is your chance to make your best case for why you're the top candidate for the position. Be concise. (But not too concise -- you'd be surprised how many people leave this field blank.)
Making Changes To Your Application: You can make changes to your application any time before the application deadline. Be sure to click 'Submit' after you're done making changes.