How do poles and zeros affect a discrete transfer function's magnitude response?

[M11]

Homework Statement

What are the effects of poles and zeros of a transfer function on its magnitude graph.
Note: The Transfer function is discrete.

Homework Equations

zeros= roots of numerator
poles=roots of denominator

The Attempt at a Solution

I really don't have any idea. I just know that the poles must be ob the left half s-plane for the system to be stable.

 

[Zryn]

http://en.wikipedia.org/wiki/Bode_plot"

Have a look at the "Rules for hand-made bode plots".