Depends on how "crunchy" you are (I know my methods aren't for everyone. LOL).
Sleep, hydration, eating your veggies - those are all crucial, of course, but wow, can they be difficult to incorporate! If you can't quite get your veggies in, make sure you take your vitamins.
As for skin, I have *always* had problem skin - cystic acne bad (I have scarring to this day) - and I've always been on a mission something to help. Several years ago, I started incorporating oil cleaning methods into my regime, and immediately started getting compliments on the textture of my skin! It sounds crazy, but it's been a lifesaver for me. I know a lot of people have to monkey with their oil mixtures (common oils are castor, olive, apricot kernal, grapeseed, and jojoba) to get the right balance, but since I've always had very, very oily skin, I use straight castor oil, and moisturise with a customised Oil of Olay bled (I mix tea tree, lavendar, and ylang ylang, with a bit of apricot kernal oil, into my OoO).
For what it's worth, I will be turning 40 in three months, and I'm often mistaken to be in my mid-20s -- by people in their mid-20s. Which to me is a ringing endorsement. *laugh*