Try to keep your teeth glittery white and remove wrinkles around the mouth (e.g. with Botox or hyaluronic acid). That alone will make you look 5 to 7 years younger.
Crooked, crowded and pigmented teeth add years, even if you are at a young age. Make sure you visit your periodontist or your dentist at least twice a year for professional cleaning and follow the oral hygiene instructions that he or she may give you, as well as any treatment recommendations, such as the need for orthodontics.