Even in British English, there is in fact only one situation where you need to use 'shall'. We use it for questions with "I" and "we" when you are making offers and suggestions. Shall I close the window? This is an offer. You think that maybe the other person is cold, and you are asking if he or she wants you to close the window. Shall we go for a coffee? This is a suggestion. You are asking the other person if they think it would be a good idea for you to go and have a coffee together. And that's all! It's that simple to use 'shall'. In all other situations, you use 'will' or - more commonly - the abbreviation " 'll" I hope that's clear. Do please ask if it's not.

They're almost the same. Shall isn't very common in American English, but it is common in British English. "I think I shall go to the cinema tonight." <- British English "I think I will go to the cinema tonight." <- American English Note: the above information isn't true when sentences begin with shall. "Shall I close the window?" = "Is it OK if I close the window?" or "Do you mind if I close the window?" In both of these examples, the person is asking for permission. They are not saying they 'will' close the window. The sentence using 'shall' is British usage.

Shall can also be used when making suggestions. "Shall we have dinner now?" But you would not say the same sentence using "will". "Will" expresses the uncertain future. If you have future plans, sure plans, then you would be better to use "be going to" or simply the present progressive.

"shall" is only used for first and second person pronouns: "I shall", "we shall" and "you shall" Will is used for third person: "she will", "he will" and "they will"