I'm 44 and look reasonably good for my age, better than when I was about 10yrs younger and in new baby fug. I do have a roundish face, which definitely counters the hollow face you can get when you are older.
I think being a healthy weight, not too fat or too thin; a healthy diet lots of veg for antioxidants, oily fish, nuts, drink lots of water... much more important than expensive creams!
Being happy and good sleep (not always possible, but I try to prioritise sleep, if I have a bad night); also meditation/relaxation/yoga all help towards a healthy, stressfree life.
Sun protection, I have worn some since I was 16, after reading how it makes you age. I am pale and so don't really bother with tanning.
Dressing to suit you, not because you are x yrs old. A strong sense of style appears "young" and not frumpy.
Several years ago I read an article where they had compared the ageing of identical twins who had led different lives, so same genes but different lifestyles. It was quite illuminating, as the main differences iirc were sun damage: one twin in a temperate climate, one in the tropics; stressful lives: longterm illness, mh problems; substance abuse: drugs, alcohol etc.