Properly cleaning the existing floor, repairing any cracks or damage, and ensuring the floor is level are key steps in preparing a basement floor for new flooring. Start by thoroughly cleaning the surface to remove any dirt, grease, or debris, and then fill in any cracks or holes with a concrete patching compound. If installing tiles or planks, it's crucial to have a flat surface, so use a self-leveling compound if necessary to create an even base.