Doctors who are truly specialized in hair transplantation are usually members of an international organization of hair restoration surgeons, such as the I.S.H.R.S.
Always ask to see their patient cases. You have every right to speak directly with former patients — ideally with cases similar to yours, with the same type of hair loss and comparable facial features.
Don’t be dazzled by celebrity photos or famous names a surgeon may have worked on. What matters most is how they’ve handled cases like yours.