Summarize:

Preschool lessons should be fun, engaging, and should involve a variety of senses and skills. In general, activities that involve rote memorization or repetition will be less interesting to preschoolers than similar activities. Spend lots of unstructured time on the playground. While these might not seem like "lessons" in the traditional sense of the word, researchers have found that free play shapes development of the prefrontal cortex during a critical period of early childhood, which has lifelong implications for emotional regulation, planning, and problem solving. Centers in the classroom should be designed to encourage imaginative, cooperative play. This can encourage role playing, turn taking, and cooperation with peers. This can increase students interpersonal skills and self-confidence.  Consider a center designed to mimic a playhouse, with a kitchen set, small toddler-sized table and chairs, baby dolls and bassinet, etc. Small, affordable toys from stores like Ikea or second hand shops can make this very affordable. Create a costume wardrobe. This can range from fancy costumes to simple silk scarves. You can often find costumes on sale right after Halloween, or simply bring creative clothing from a second hand store like overalls, a fancy princess dress, a cowboy hat, any type of uniform, etc. Plush stuffed animal toys are often the beginning of many creative games for preschoolers. Children can use their imagination to pretend that these are students in a classroom, pets in a home, animals in a rescue center or veterinary clinic, etc. Choose toys that you can easily wash every few months in a washing machine. This can often be difficult in large classes, but find a way to spend time with each child either daily or weekly, engaging in a small game or one-on-one reading time. Studies show that adult interaction is crucial for developing confidence and early literacy skills. It also reinforces the student-teacher bond which makes a child feel safer and more secure in school. In addition to one-on-one time, consider inviting parent volunteers to read to children once a week in small groups. The number of volunteers you get can determine the size of the groups; anything from one-on-one to groups of five students per adult will foster relationships and discussion that are key to early literacy.
Remember that the most developmentally appropriate way for small children to learn is through play. Build a classroom around the idea of play. Build in adult interaction.