Your application would be strengthened by:
(a) lab courses and others (e.g., directed studies) that provide research experience in Psychology
(b) strong letters of reference from professors familiar with your research experience and aptitude.
(c) excellent performance in courses on methods and statistics in Psychology
(d) a good distribution of courses across the breadth of sub-disciplines within psychology
(e) strong grades (>80%) are more important than the actual courses