You first need to clean the unit thoroughly and ensure no dirt or debris is left on it. Once you're done cleaning the unit, wrap it up in moving blankets or old towels and secure them in place with duct tape. Then, place the unit in a box that's slightly larger than it and fill any space with packing peanuts or crumpled-up newspaper. Finally, seal up the box and label it clearly so you know not to open it until you're ready to install the air conditioner.