I work in a center for children with developmental disorders and the answer, in my opinion, is the same across the board for this population as well as many others- active play. It is essential during these early childhood periods that the child is provided with unlimited opportunities for active play. This might include playground equipment, an arts and crafts table, a gaming table, and plenty of access to books and sunlight. Television, computer and video games- while some might provide supplemental early learning- are typically not conducive to developing those essential skills. Running around, inventing games, socializing with other children, and strengthening abilities such as reading and arithmetic are really great places to start.
Hope this helps! Have a wonderful day.