Cinderella shall go to the ball

It must be a hundred years since anyone cared greatly about the distinction between shall and will. It doesn’t matter much in speech or informal writing because either word often becomes ‘ll anyway, and in most contexts using the “wrong” one will rarely cause even the most fastidious pedant to fustigate. Sometimes the right one is obvious anyway, as with the will in the previous sentence: shall would sound silly there.

But if you want to be fussy and remind yourself of the rule that most of us vaguely observe but haven’t really thought about, English text-books state that that to express the ‘plain’ future shall is used in the first person and will in the second and third. Thus, these are prophecies:
I shall go
You will go
He will go
…while if it is a matter of volition or obligation, it is the other way round:
I will go (I am determined to go, or I intend to go)
You shall go (you must go, or you are permitted to go)
He shall go (he must go, or he is permitted to go)

In the admirable Complete Plain Words (the whole text of which is here) Ernest Gowers points out that the Celts are different (well, we knew that, didn’t we?). They have never recognised I shall go, hence the very old story about the drowning Scot who was misunderstood by the English onlookers and left to his fate because he cried ‘I will drown and nobody shall save me’.
American practice follows the Celtic and we tend to follow the Americans, so we can no longer say dogmatically that ‘I will go’ for the plain future is wrong, or, smugly with the nineteenth-century Dean Alford, that:
I never knew an Englishman who misplaced shall and will; I have hardly ever known an Irishman or Scotsman who did not misplace them sometimes.

That’s quite enough of all that. Except, of course, for those who really want to know more. The King’s English (the invaluable bartleby.com gives the whole text of the 1908 edition here) has twenty pages on shall/will, introduced by this paragraph:
It is unfortunate that the idiomatic use, while it comes by nature to southern Englishmen (who will find most of this section superfluous), is so complicated that those who are not to the manner born can hardly acquire it, and for them the section is in danger of being useless. In apology for the lengths of these remarks it must be said that the short and simple directions often given are worse than useless. The observant reader soon loses faith in them from their constant failure to take him right; and the unobservant is the victim of false security.
These immensely patronising words certainly put northerners, Johnny Foreigner and the ill-born in their place; but they were written a hundred years ago: modern Wikipedia points out that the book is rather dated, deals exclusively with British English usage and that readers should be aware that its attitude to 'Americanisms' reflects the age in which it was written.

For those who really really want to know all about it, the OED (now free online to all Englishmen and even Englishwomen) has 20,464 words on shall and 22,811 on will, including the quotations. Reading them all is no mean task, but not without its rewards: for example, if you get as far as Section 52 on will, you can learn that there is a Lancashire dialect phrase wilto shalto (wilt thou, shalt thou), meaning whether voluntarily or by compulsion. This has become our willy-nilly. Its use is illustrated by the following quotation from an 1857 book on Lancashire:
There is at'll believe naught at o', iv it isn't fair druvven into um, wilto, shalto.
This is a charming pronouncement; I have just about worked out what it means, that I ‘ave, and I await an opportunity of introducing it into a conversation and a thissens producing a stunned silence.