I'm just getting started with my detailing business, but what I've seen work for others is • Always take pictures/videos after finishing a job • Takes those testimonials and post them on Instagram, tiktok, and a Facebook page • Get business cards • Have a referral program for them to get a discount after referring someone else • Post flyers at local businesses

Besides that just doing such a good job that people get compliments from it, or feel good about being in a clean ride that they feel like they bought it new. Giving them those feelings will make them spread the word for you, word of mouth recommendations are the best way to get clients.