Those little marks you put in sentences that are called "punctuation" may not seem all that important, but a misplaced comma or semicolon can totally alter the intended meaning of a sentence.
1. Add and remove commas to see how they affect the sentence. For example, "Let`s eat, everyone" becomes "Let`s eat everyone" - changing the meaning of the sentence from a pleasant call to dinner to an expression of cannibalistic tendencies.
2. Add a question mark to the end of a sentence to change the tone. For example, a simple statement like, "He didn`t mean to kill her" goes from an expression of confidence in the individual to a question meant for interrogation: "He didn`t mean to kill her?"