Speak slowly and calmly at all times. Preschoolers get cues about the situation from your voice. If you're speaking quickly and loudly, children may get agitated and fail to pay attention to what you're saying.
Give one direction a time. Preschoolers may struggle to process a multi-step instruction, preventing them from completing any part of it. Before beginning a project, explain in broad terms what you're going to do, then break it down into one step at a time. Wait until the children have completed one step, before giving another direction.
Create a section of the classroom that's free of distractions. This area is where you will meet with students when they need to focus, such as when you're explaining a new project or talking about classroom rules. Don't hang any colorful posters or signs in this area, and block it from the rest of the room with bookshelves if possible. If children don't have access to toys or anything interesting to look at, they'll be able to focus on only you.
Use props. Visual cues may be easier for preschoolers to understand than verbal ones. Choose a squishy ball or a bean bag and explain to children that whenever you're holding the ball, all eyes should be on you.
Choose a prop for children to use as well. Preschoolers often struggle to wait for a turn to speak, so use another squishy ball as the "time to talk" ball. Pass the ball to children who want to speak, and ask all other students to listen. If each child knows she'll get a turn to speak, she won't be distracted by worry about being heard.
Lead children in movement activities once every 30 minutes. Preschoolers have a lot of energy and will become antsy, if they're forced to sit still for too long. Allowing children to do jumping jacks or dance for a few minutes first will help keep them focused on quiet, seated activities.