There are 8 core principles to

non-directive play therapy:

1. The relationship with the child and the therapist must be warm and supportive.
2. The child unconditionally accepts the therapist.
3. The therapist unconditionally accepts the child.
4. The therapist allows the child to freely express their emotions and believes that the child is able to find and solve problems.
5. The therapist depends on the child to find their solutions.
6. The therapist repeats the child's words and play providing direction.
7. The therapist allows the child to read and determine the pace of therapy.
8. The therapist only sets limits to keep therapy safe and base in reality.

-Axline, V. Play Therapy. New York: Ballantine, 1947. Print.