It is similar to "j" in Enlgish. However, you must put the tongue behind the TOP row of teeth. On releasing, the tongue is pulled backward a little. Do not blow the following vowel sound outward. Try it. Anyhow, there are gadzillions of Chinese in Oz. They can tell you if you get it right.

中文. To us non native speakers it sounds closer to jongwen. I saw it described once as similar to the g in merger. It is a non aspirated ch sound. Hope this helps :D

OK, the pronouncation is deffrenct between "zh" and "z", when you say "zh", you should bend your tongue, the tip of your tongue should touch your dedendum, when you say "z", your tongue shoud be straight. 'ch" and "c", "sh" and "s" are the same action. I know it's so difficult for you , also difficult for some native Chinese , for example,the people in my hometown couldn't seperate "zh, sh, ch" from " z, c s". Work hard , Luke , i think you can do well , you are a smart guy !

Yeah, I find I have trouble with understanding chinese speakers who pronounce shi as si. I've noticed Taiwanese speakers often say it that way.

Thanks guys! - It sounds like a regional issue. I will be studying with my teacher nearer to Beijing tonight. This issue came up with my teacher based in Shanghai. I am very happy with both teachers so there may be some differences I have to get used too. I hope I can find a way of pronouncing "zh" to keep both teachers happy! - Otherwise I will change pronounciation based on the teacher which is somewhat confusing!