Relevant experience for clinical psychology training would require some substantial contact with clients of mental health services, but also working psychologically. That can be doing audits and evaluations,psycho-education, neuropsychological assessments, working therapeutically with clients using psychological methods. In terms of how long you do it, most courses specify at least a minimum of 1 year, but bear in mind most clinical trainees start their training in their mid to late 20s.
Meeting and greeting is a so-so first step, but something like being a Health Care Assistant, or Nursing Auxiliary would be even better.