Some assignments will include "extra credit" sections. These will enrich your understanding of the material, but deliberately will provide scant credit in proportion to the work required. Do them for what you'll learn beyond the basics, not the points, and don't even think about starting the extra credit portion until the main problems are complete.
For practice exams, see previous offerings of the course, in particular for Autumn 2006 and Autumn 2008. The mini-exercises are also good study material.
You can email all the TAs and the instructor at cse341-staff at cs.