Download and read the PDF article titled: The Standard of Teaching: Catechesis in the RCIA Catechumenate Period to find the answer to the question: What do I teach and when should I teach it?
A quote from the above article:
"Catechesis cannot be considered systematic and organic solely because it covers a great deal of material or is lengthy. A defining characteristic of a systematic and organic catechesis is its presentation according to the hierarchy of truths (see CCC 90, 234; GDC 114-115). Participants need to understand certain truths first in order to be able to understand others, and as catechesis proceeds, each truth needs to be linked to those taught previously."
An example: In their catechesis, the catechumens and candidates must come to understand the person and work of Jesus before they explore the Marian dogmas. Then, when Mary is presented, her Immaculate Conception, Perpetual Virginity, Divine Motherhood, and Assumption are shown to have relevance insofar as to who her Divine Son is and what his plan is for her. "What the Catholic faith believes about Mary is based on what it believes about Christ, and what it teaches about Mary illumines in turn its faith in Christ" (Catechism of the Catholic Church, #487).
Related Blog Entry
Also, see the blog entry titled: "Analyzing Doctrines - What to Teach"