How to determine correct punctuation

How are we to guess at correct punctuation?  Unless you can remember the entire speech, it is sometimes difficult to tell whether a section should end with a comma, a period or an exclamation point.  (And, actually, the sentence beginning "Paul va prendre sa voiture..." is a declarative sentence and not a question.) I have not been counting myself off where such punctuation is concerned because there seems to be no definite way to determine what the correct punctuation should be.