I would like to know when to use the words "shall" or "will" when refering to the future. Is it that I can choose either of the words or is there a rule to the usage?
Can you help please? Thanks much.
There's an error in what davidsk's post. What he meant to write is that "shall" can be substituted for "will" with first-person subjects, not objects.

If you are in the U.S., or talking or writing to Americans, you can drop "shall" completely and use only "will". To Americans, "shall" sounds snobbish and is rarely used.
"Shall" is used on the object is first person
"will" can be used in all cases, first, second, third person as an object.

For example:
Shall I return this book to you tomorrow?
We shall get up early tomorrow morning to catch the 0630 train.
 taiwandave's reply was promoted to an answer.