Would is normally used when you say "I would like to go to the store" or "I would go to the store if I had money". It is used to express something you desire to do.

Should is used when you say "I should have went to sleep earlier" or "I should be doing my homework". It is used to express something you are supposed to be doing.

Shall (that is spelled with an 'a") is used when you say "I shall be at dinner at nine" or "We shall go to class now". It is used to express something that you are definitely going to do. However, shall is not used often. We would normally say "I will be at dinner at nine" or "We will go to class now".

Hope this helps you!

Thank You so much. <img title="Smile" src="http://www.italki.com/Scripts/tinymce/jscripts/tiny_mce/plugins/emotions/img/smiley-smile.gif" alt="Smile" border="0" />