"I will" or "I shall" [duplicate]

From 'The Cambridge Guide to English Usage':

Will is now the standard choice for expressing future plans and expectations, everywhere in the world. Shall is stylistically marked with volitional meaning in legal and regulatory statements, and expresses politeness in first person questions.

From Fowler's Modern English Usage:

In the first person 'shall has, from the early ME period, been the normal auxiliary for expressing mere futurity without any adventitious notion'.

It then carries on for two full pages of fine print.

The short version is that if the subject is "I" or "we", and the sentence is not a question, then "shall" has traditionally been correct, and "will" has traditionally expressed a level of determination, or a promise. Today though, the two are interchangeable. I tend to use "shall" (note that I am neither British nor American); many people tend to use "will".

If the subject is NOT "I" or "we", then the future tense has "will". In this case, "shall" means something more like "must" - that is, the Old Testament sentence "you shall not kill" is a commandment, not a prediction of the future.

If the subject is "I" or "we", and the sentence is a question, then "shall" is an offer or a suggestion ("shall we dance?", "shall I pay for dinner?"); but "will" is asking what is going to happen.

In modern (non-legal) American English, the modal auxiliary shall is not used, except in two idiomatic constructions, both first person, both questions, and both involving invitations and offers:

Plural Shall we? can occur alone as a tag for an invitation starting with Let's:

• Let's take a walk around the lake, shall we?

and can also start a question signalling a request for cooperation and agreement:

• Shall we consider the matter closed, then?

Singular Shall I? occurs in similar situations, as a tag for an offer starting with Let me (though not with Let's, which is plural).

• Lemme just see what I can do, shall I?

or starting off a question that conveys an offer:

• Shall I fix the door so it doesn't squeak?

Other than those constructions, any use of shall by a native speaker of American English is being read aloud (or is being recited from memory) from an archaic formal, written source (e.g, Congress shall make no law ..., Thou shalt not ...).