The answer to 'best way to clean grout' is to use a grout brush and a grout cleaning solution. First, sweep or vacuum the grout lines to remove any loose dirt or debris. Then, mix a grout cleaning solution according to the product instructions, usually a mild detergent or acidic cleaner. Use the grout brush to scrub the solution into the grout lines, working in small sections. Let the solution sit for the recommended time, then rinse the area with clean water. For tough stains, you may need to let the solution sit for a few minutes before scrubbing. Be sure to wear gloves and work in a well-ventilated area when using chemical cleaners.
Regular grout cleaning is important to maintain the appearance and prevent discoloration or mold growth. Depending on the amount of foot traffic, grout should be cleaned every 6-12 months. For heavily used areas, you may need to clean more frequently.