Seeing a therapist for the first time, 30 years old. - eviltoast

What should I say or not say to the therapist for the first time? Should I come out and say I think I have ADHD or should I avoid my own self-diagnosis and ask them to evaluate my habits on their own? Anything I should say or not say in a first chat? Anything that may be a red flag or green flag with a new therapist?