For your tests, be sure to look up exercises on the following.  Know how to recognize and how to avoid errors in these grammatical points, or, how to use these grammatical elements correctly.  These represent the most-asked-about items on tests.

• Review all "Parts of Speech" exercises
• Subject-Verb Agreement (if you need a lot of help with this using simple but effective examples, see my "Simple Subject-Verb
  Agreement" exercises link)
• Commas (practice all)
• Capitalization (especially of proper names and places)
• Comma errors (commas with appositives especially)
• Commonly misspelled words (Its/It's, Too/Two/To, Lose/Loose, etc.)
• Punctuation in the Greetings of Letters (using colons with business letters)
• Semicolons
• Colons
• End punctuation
• Question Marks
• Quotation Marks (punctuating dialogue especially)
• Italics (punctuating titles especially)
• Pronoun antecedent agreement (Lesson 22 especially)
• Possessive pronouns
• Possessive punctuation
• Apostrophes
  
  
  Easy-to-search archives of grammar practice:
  http://www.dailygrammar.com/archive.html