Dave O: 'I don't find the difference between "shall" and "will" ... at all daunting in concept.'

I wonder: if you tried reading the relevant pages in "The King's English" would you still feel that way? I believe the issue is more complicated and subtle than you think.

I read it long ago, and here's what I think I have retained:

In the first person, "I/We will" indicates personal choice (or an act of will, if you will) while "I/We shall" indicates that the matter is beyond my/our control.

"I will bring you a cup of tea" is correct (I choose to do it; I am willing to do it).

"I shall be 63 on my next birthday" is correct (I can't help it; it will happen whether I like it or not).

"I think we shall have rain today; therefore, I will bring my umbrella."
(I have no control over the rain; bringing an umbrella is my choice.)

In the second or third person, things get turned around.

"Thou shalt not steal" is correct. God is speaking the second person. It is God's will that we humans should not steal.

"You shall finish your homework before bedtime!" (I insist.)

"...but you will keep dawdling!" (You are defying me; we are having a battle of wills.)

"Should" and "would" are the subjunctives of "shall" and "will".

"If I should die before I wake" is correct. (I don't want to die, but in case it happens anyway....)

In the above usage "should" does not imply "ought to"—but that's how we Americans usually use "should" today:

"I shouldn't have another cookie" = "I ought to forego it"

Mind you, I don't claim to always follow these rules myself—most of the time I don't even try—but I find it interesting to know about them.