The answer to 'how to clean drain' is to use a combination of mechanical and chemical methods to clear clogs and buildup in your drains. Start by removing any visible debris or hair from the drain opening using a pair of pliers or a drain snake. Then, pour a baking soda and vinegar solution down the drain, let it fizz for a few minutes, and flush with hot water. For tougher clogs, use a drain cleaner product or rent a motorized drain snake from a hardware store. Be sure to follow the product instructions carefully and ventilate the area well.
Regular drain cleaning every few months can help prevent major clogs and keep your plumbing system running smoothly. However, if you're unable to clear a stubborn clog or notice signs of a more serious issue like slow draining or foul odors, it's best to call a professional plumber for assistance.