Explain the basic components of a sentence to second graders. Teach them that sentences must contain a verb that describes an action, a subject that describes who or what is taking the action, and an object that indicates what the action is affecting.
Show students how to put these basic components together to form a beginner sentence. For example, write the sentence "Jenny ate her sandwich" and explain that "Jenny" is the subject, "ate" is the verb and "sandwich" is the object.
Ask each student to write her own sentence and label the subject, verb and object. Ask students to correct each other's work to ensure that they have internalized the lesson.
Move on to more complex structures, such as compound sentences. Teach students that two phrases that can be written as separate sentences can be joined by words called conjunctions, such as "and" or "but."
Provide students with plenty of review so that they internalize the structure and form of beginning sentences.