According to the Oxford A—Z of Grammar & Punctuation by John Seely, there are three rules.
- Use shall with I and we
- Use will with all other persons (i.e. 2nd and 3rd person, singular and plural)
- Reverse this for emphasis (‘The sea shall not have them.’)
Interestingly shall is most often used in questions, such as Shall we dance? In most cases now though people use will in conversation. Seely claims that will is used ‘fourteen more times more frequently than shall’. And it seems that shall is more common in British English than in American English.
When it comes to asking for advice there’s another difference between British and American English.
In British English shall is used to ask for advice.
- Which way shall we go?
The American version of English prefers should.
- Which way should we go?
Somehow though, I can’t quite get my head around Should we dance? And, of course, both of these are more commonly replaced in spoken English by that marvellously lazy contraction Wanna. (e.g. Wanna dance?)