First I gather information. You are the only person who knows everything about you. I ask a lot of questions about medical history, weight history, and eating history. I want to know what has worked for you in the past and what has not. You will leave our first visit with a goal to work on, even if it's not a full blown meal plan. Most people have several visits to establish/evaluate goals and to review their food intake (either via a food journal or by doing a recall in the office).
I became a registered dietitian because I wanted to work with evidence-based nutrition recommendations. We are super-saturated with nutrition messages and I wondered, what do we really have to be worried about? I acknowledge that all good ideas started on the fringe, but part of individualizing recommendations is to know where someone has been before telling them where to go next. Look for horses before you start looking for zebras.
A registered dietitian has has a lot of standardized training in nutrition and specific-diets intended to manage or treat specific conditions. Each is different in the level of functional medicine they practice and their levels of skill. A nutritionist is not trained the same way and can be helpful in overall health coaching or many cases of weight management. Dietitians are less likely to be practicing complementary and alternative medicines or using little tested theories as a first-line treatment.
Think about what you want from the experience. Where are your beliefs and biases? How has the issue you would like to discuss developed over time? Are you already convinced of something or looking to explore? What is the time frame for which you expect change or resolution? What is your media "intake" like? How does that influence your view of nutrition, weight, and health?.