Use of the word "shall"

I keep reading the word "shall" used incorrectly.

My advice is: don't use the word "shall" at all. 

Native speakers don't use this word that often, so why risk using it incorrectly when you can live without it?

Origin of the confusion:

The word "shall" sounds a lot like the German word "soll". 

The German word "soll" usually means "should" in English.

Greenhouse gas emissions should be reduced by 20% by 2020.

Treibhausgasemissionen sollen bis 2020 um 20% reduziert werden.

What time should be meet tomorrow?

Um wie viel Uhr sollen wir uns morgen treffen?

Another source of confusion is the 10 commandments, which in English are "you shall not" and in German "du sollst nicht". But it means "you will not" as opposed to "you should not".

Correct use:

"Shall" can be used in questions and for talking in the future tense instead of "will".

For example: 

Question:  "Shall we have a cup of tea?"

Instead of will:  "I shall bring cake tomorrow!"