I am wondering about which part of a mouth to be used to make a english sound.

Today, my classmate and I discussed about it, but all of us had a different opinion.

a guy answers the question that "front of a mouth", a guy answers the question that "back of a mouth", a guy answers that "use the chest for making thick english sound as well as use a head to make a english sound" a guy answers the question that "use the nose to make a english sound"..

but I think those answers got a point.

Some americans more use nose and a front part of a mouth to make a sound, some of them also use a chest and a back part of a mouth to make a thick and lower sound.

I am just wondering .. and I try to find it out but I didnt. that's why I am asking that question here.

Is there anyone who can show me the way to solve this trick problem?

Thank you in advance.
All of these are used to make sounds. I don't think any one of them is more important than the others. To speak English all of these must be used in coordinated patterns. There is no trick to it. It's just a matter of practicing a lot, especially by imitating the sounds of native speakers, so that the muscles in your tongue and lips and throat become accustomed to moving in the ways that are special to English.

An excellent guide to the areas of the mouth that are used is [url=http://www.uiowa.edu/~acadtech/phonetics /#]Phonetics: The Sounds of English and Spanish[/url]. It has flash animations showing what each part of the mouth is doing for each sound. Some of the wording is a little technical, but the animation should "give you the picture".