Looking young: the latest from the science of aging

What makes us look younger than our years, or conversely, what ages us beyond what we would prefer?

Jane Brody summarized some of the most recent research into what works, and what doesn't, when it comes to keeping a youthful appearance -- something we just can't seem to help caring about.
Factors that can make you look older: smoking, sun exposure, excessive stress, and taking anti-depressants.
Other interesting tidbits:
If you're over 40, a higher BMI makes you look younger, because fat fills in facial wrinkles. (We knew that, right?) What she doesn't address is at what point plumpness becomes unhealthful enough that the wrinkle filler isn't worth it.
People who smile and laugh a lot look younger than those who have more dour countenances.
Strength training is more important than aerobic exercise in making us look fit, healthy and yes, younger.