I teach one to one all the time. There are some lesson ideas on daves eslcafe for one to one. But really it is a lot easier in some respects than class lessons. Start by asking questions about the student's life, experiences etc. Questions that don't give you a yes or no answer. i.e. Do you find English difficult? (yes/no) better to ask In what way do you find English difficult? If even this is too complicated, go back to yes/no options to build confidence. Have a load of questions, from easy to hard and use them as a jumping off point. As difficulties arise, in grammar, pronunciation, understanding, just mark them down then you can look at them later and build some lessons around the grammar points.
Your question really is too big to answer here, but if you go very slowly, speak clearly without jargon, and allow the silences for the student to think about what you said and questions you ask, it will be a good beginning. By the second lesson you will have a good idea of what you're up against and will be able to come up with some fun lesson plans that are of interest to that specific student. Best of luck...and be patient!