I'd add to staying out of the sun: find a good moisturizer and use it faithfully. I also do a mild exfoliation two or three times a week, and it has done wonders for my skin. I have a friend who was a dedicated tanner in her teens and 20s and now she looks at least 10 years older than she actually is. So definitely stay out of the sun!
Most beauty secrets really are based on common sense. Some are a little more exotic than others, but the majority are good sense: drink a lot of water, stay out of the sun, cleanse and moisturize daily. It's the little, simple things that accumulate and lead to great-looking skin in the long term. I