Learn as much as you can about the entire field of psychology. There are many sub-specialties to consider. When people say "I want to be psychologist," general they're thinking of clinical psychology -- where you sit down with one or two people and hack away at the subconscious. However, there are a bunch of different branches and all are worth exploring early on:
Organizational and industrial psychology: the study of human psychology in industrial work environments and large organizations.
Clinical psychology: the study of human psychology in clinical settings like hospitals and mental heath facilities, including psychotherapy.
Cognitive psychology: the study of internal thought processes such as problem-solving, memory, perception, and speech.
Neuropsychology: the study of the brain and larger nervous system and how they contribute to human psychology and behaviour.