You control the quality of your tone through your embouchure and your breath. There are other factors - the saxophone, mouthpiece, ligature and reed - but the primary areas where you control the tone are embouchure and breath control.

Embouchure

Embouchure is the position of the mouth on the mouthpiece.
Here is a page that has checkpoints and exercises for developing a good embouchure.

Breath

How well you use your breath affects every element in your saxophone playing.
Here is a page that describes the use of the breath and provides exercises for developing breath control.

Playing a wind instrument requires developing a very agile tongue.
Here is a page that contains checkpoints and exercises for developing your tonguing.

Technique development is the process of becoming fluent in the vocabulary of music: scales, intervals, arpeggios.
Here is a page that provides exercises for technique development.