To clean the Bialetti Moka Express, you should disassemble the coffee maker and wash the parts with warm water and mild detergent. Avoid using abrasive sponges or cleaners as they may damage the aluminum finish. Dry all parts thoroughly before reassembling the Moka Express. It is also recommended to periodically descale the coffee maker by soaking it in a solution of water and vinegar to remove any built-up coffee residue.