Besides the things mentioned, your hairstyle, attire, dry skin,
late sleeping, no maintaining of your face, and personally... how
you feel on the inside. If you feel old, no matter how young you
can look, people can see you are old.
So to start off, get a younger looking hairstyle that SUITS YOU.
Then get some new clothings that makes you look more vibrant and
young (I am sure you have friends who are fashion experts), buy
those skin care, moisturisers and use it daily, change your
sleeping habit to 10pm or so and start mingling more with young
people. I do NOT say you have to abandon your friends, I meant go
out more with those "young" ones, observe them, see why they can be
so energetic and vibrant.
Slowly but surely, you will start to see yourself feeling younger
and being confident that you are young. Its quite an expensive make
over, but if you want to be young, you should try all possible
ways. 
