It there's one golden rule to prolonging your tan, it's to hydrate your skin. After-sun, dry oil, butter or balm... All of these will nourish your skin and prevent peeling. This particularly applies to your face, which will have been battered by sun, salt, chlorine, heat and wind. You should also hydrate from the inside out. Aim to drink 1.5 litres of non-alcoholic beverages a day, even if you're not thirsty: water, tea and herbal/fruit teas will do the trick.
Give your face and body a weekly scrub. Scrubbing gets rid of dead cells that suffocate skin and give us dull complexions. Don't use a coarse scrub as it'll damage the epidermis - go easy on yourself! A gentle scrub won't strip off tanned skin cells, so you'll keep your golden glow for longer.
Two weeks after you're back from holiday, start applying a fake tan. Make sure you choose the right shade and apply it uniformly, so as to avoid darker patches and streaks. No need to go overboard with the amount you apply. Take advantage of sunny days to keep your golden glow: going for a walk, eating outdoors or enjoying a morning jog will help prolong your tan.