Expose the students to example sentences containing the grammar rule you are teaching. You might choose to do this with a reading, a recording of a conversation or a video. When teaching the past simple tense, for example, you might choose to use newspaper articles as these commonly use the past tense.
Ask students questions that will them allow them to deduce the meaning of example sentences. When teaching the "going to" structure with an example sentence such as "He is going to eat lunch," for example, ask students, "Does he plan to eat lunch?" "When does he plan to eat lunch?" In this manner you can guide the students to determine that "going to" is used for future plans.
Write an example sentence which uses the grammar rule you are teaching on the whiteboard or blackboard. Ask the students to identify the different parts of the sentence. For example if you have written a present perfect sentence on the board such as, "He has eaten," students should identify a subject, present form of "have" and a past participle verb.
Give students a set of approximately ten sentences demonstrating the grammar rule but with words missing. Students complete the sentences by filling in the missing words. Ask students to check their work in pairs or groups before going over the sentences as a class.
Give students an activity which encourages them to use the grammar rule you are studying. When, for example, teaching the grammar rule for the present continuous tense, you might ask each student to write three example sentences using the present continuous, starting with "I am." Circulate as the students work giving help when necessary. Arrange the class into groups of three and ask the students to take turns miming their sentences. The other students should try to guess, in English, what the student is miming. For example, "You are swimming," "You are eating," "You are making breakfast."