Assess what level of English speaking and comprehension your students now have. That will tell you such things as what level of vocabulary you can use in early lessons, how much grammar you will have to teach, how complex your instructions can be and how fast you can talk to your students.
Use visual aids. Anything with interesting pictures can be helpful. You can get a lot of mileage out of magazines, newspapers and Internet images. Pictures can help you teach vocabulary and conversation skills.
Make a verb chart. Use it to show the present, past and part participle forms of verbs as well as how verb tenses work in English. Supplement the chart with a lot of oral examples using verbs in their various forms. You probably want to devote more time in your sessions to conversational skills than to grammar, but an understanding of how English verbs work is crucial.
Spend part of each lesson talking about some major aspect of American life. Mixing in cultural background sessions will provide you with a context for introducing a lot of important vocabulary and idioms. Topics for each segment could include real estate in America, dating customs, the education system, college life and the duties of the U. S. president. You don't have to spend a lot of time preparing these segments. Just jot down a rough outline of salient points of the topic and give a little thought to how you will develop the topic. During the session, encourage your students to ask questions or to stop you whenever you say something they don't understand.
Provide one segment in each session in which your students do most of the talking without your correcting them on anything. Just let the conversation flow, so they can get comfortable using English in a conversation.
Ask your students plenty of questions. The more you can get them talking the better. Their answers also will give you input on how much of what you have been teaching they are absorbing.