Use a textbook that has several different elements of grammar, including written and spoken grammar. A basic grammar textbook has chapters with information, spelling lists and exercises that students can complete. Use the textbook as a guide, however, do not rely completely on the textbook, as adults may get bored.
Choose a topic for each class meeting. Appropriate topics include using contractions correctly, matching the tenses of verbs and subjects to each other, avoiding common mistakes such as saying "ain't,", and using correct grammar and spelling in writing.
Have conversations each time your class meets. When adult students are able to talk to each other, and talk to you as a teacher, they are more likely to pick up subtle lessons on grammar and the correct way to use words in context.
Create both oral and written lessons, quizzes and exams. Grammar should be both oral and written; adult learners appreciate the chance to practice by both writing and speaking.