Pinyin initials z, c, s

Tips of how to pronounce ' z ' :
First, the tip of your tongue reaches forward to touch the back of your upper teeth. Then you lose the contact and blow the air through the narrow gap between your tongue tip and the back of your upper teeth to make the sound.

As for ' c ', the tip is the same as ' z ', but you need to blow the air harder.

Tip of how to pronounce ' s ' :
First, the tip of your tongue reaches forward to be close to the back of your upper teeth. Then you blow air through the gap between them to make the sound.