Dear Alister,

Thank you for your further questions.
RFrith has answered your questions very well. Here are a few examples to add.

xie2 鞋 （ Mandarin ） hai2zi 孩子 （Sichuan dialect )
qu2 diao4 渠道 （Mandarin） guan3diao4 管道 （Taiwan dialect )

As for grammar,
我先走。 （Mandarin） 我行先。（ Cantonese， adverbs after verbs ）
你吃饭了吗？ （Mandarin ） 侬饭吃过勿？（Shanghai dialect, nouns as objects
before verbs ）
In terms of pronunciation,
Hu2 湖 （Mandarin ） Wu2 湖 （Cantonese )
pao3 跑 （Mandarin ） bo2 跑 （Shanghai dialect)

Above is only a tiny part of the difference between Mandarin and dialects, as examples.

Thank you for your article, Peter.  After your introduction, your first piece of advice is the following:

"Start by finding a professional teacher who speaks standard, native Chinese."

This raises three questions.

First, what exactly is "standard, native Chinese"?  Do you mean a Chinese person who speaks Mandarin using a northern accent?  Or do you mean something else?

Second, how can a native English person identify a teacher who speaks "standard, native Chinese"?  Almost every teacher writes that he or she speaks standard Chinese.  What questions can a student ask? For what sounds should a student listen?

Third, what is the harm in learning non-standard Chinese?  I don't mean a non-standard, region-specific dialect.  I mean, if the northern accent is the 'standard', what harm is there in learning the southern accent?

Thank you for any further advice you are able to share.

Absolutely, Andy.

i am an Chinese,in my opinion,just like learning  a aonther language you just need spaeking at everytime  and don't be shy,in this way your oral Chinese must be improved,that's my ideal,thanks