Often students will say they just want conversation. This is fine but you will still need to plan for it. Talking is good but for conversation to be effective you need to structure it.
Prepare your topic and make sure the content and language level is right for your student. Don't improvise! You may get away with it once or twice but after that your lessons will slowly come apart.
Collect all the necessary materials. If you are not using a book and rely on handouts make sure you have copies for both yourself and the student.
To do all this successfully carry out a needs analysis