Dr. Harold William Halbert
Consider this incorrect sentence:
If you cook Grandma will do the dishes.
Now break it down:
If you cook Grandma will do the dishes.
Introductory element Subject Verb phrase.
Need a comma between an introductory element of more than three words and the subject/independent clause.
If you cook COMMMA Grandma will do the dishes.
It can be helpful to visualize a sentence with an introductory element without words:
___________________ COMMA ____________________________Period
We can get a bit more specific about how this formula works:
[introductory element that sets up condition or a transition] COMMA [Subject that does the action of the sentence] [verb phrase that is the action of the sentence]