Start by removing the car mats, in order to thoroughly hoover the carpet, as well as the seats and the boot. You should then turn your focus to any stains currently on the upholstery of the car, and do your best to deal with them. If it's not possible to remove certain ones, forget about them for the time being, and clean the interior hard surfaces and windows. Lastly, apply the air con bomb cleaner and the stain protection spray. If you're not fully satisfied with the end-results, consider calling in your local mobile interior detailers.