They need many opportunities to explore the space around them as an important training ground for future learning. Select toys with care because most of the modern gadgets are just that, offering little opportunity for useful play. Take your youngster out of the house to explore its immediate environment. Expand the circle of exploration with walks in the park, swimming in the pool, shopping trips to the mall, etc. Third, attention and concentration.
Children have notoriously short attention spans.
Mom, I'm bored. Such moans usually indicate lack of attention and inability to concentrate, and tend to become patterns and habits if ignored. Children must be trained in this, and consistently so. Check the expectations of the school. Schools will have a set of expectations for their incoming children.