I was discussing this very topic with my 11 year old this morning. He doesn't want to ever be a teenager and has decided to lie about his age in order to avoid going to middle school. (Also, teenagers are evil.)  I tried lying about my age in order to avoid becoming middle aged but it didn't work. Some more practical suggestions are:
- Don't drink excessively.
- Don't smoke at all.
- Sunscreen, sunscreen, sunscreen.
- Retin A but I don't know when it becomes necessary. In your 30s perhaps?
- Extreme weight loss or gain can be hard on your skin. I think we'd all like to lose some weight but avoid the yo-yo cycle, especially if you're gaining and losing significant amounts. 
- Exercise is good but remember to protect your skin from the elements if you're outside. I put a layer of Nivea on before I go for my walk in addition to sunscreen this time of year.
- I think the "8 glasses of water a day" thing is currently out of favor but it's already been pounded into my head so I still do it. It also helps avoid urinary tract infections.
- I use a cotton pillow case but I change it every few days mostly because I like the smell of a clean, freshly ironed pillow case. It has just occurred to me that I use chamomille water when ironing my sheets (yes, I really iron my sheets) because it's soothing but is it possibly an irritant?
I tried to make myself sleep on my back but I couldn't do it. My husband sleeps on his back with his arms crossed. You'd think he was dead if it weren't for the snoring.
 
 
 
 

Hi
I was wondering about the satin pillowcase, that does have any scientific support? It probably feels nice, but what's the problem with cotton ones?
I have to say excercise!! , there is increasing scientific data about its benefits, beyond weight control, it gives you energy, it improves your mood, reduces stress as well as reducing your risk of diabetes and heart disease
however after some years on the fitness industry, not every workout is created equally, so here are my tips for working out to age gracefully (preventing aging sounds a litlle bit weird to me);
- do some type of activity 30 min a day (house chores do count)
- do something that gets your heart pumping at least 3 times a week for at least 30 minutes (but don't beat yourself up if one week you couldn't)
-be gentle on your joints,wear good shoes and change them every 3-5 months, 1 hour of kickboxing every day is a recipe for knee problems later on
- do resistance training, it strengthens your muscles AND your bones (it prevenst osteoporosis)
-develop the body in a balanced way, do not work only the muscles you see in the mirror, and stretch, having a bigger range of motion keeps your limber
-develop a strong core, it will keep your spine healthy and give you  nice posture (instant slimming!!)
- workout mindfully, pay attention to what you are doing and challenge your coordination  and your balance (it keeps your brain younger)
 
and of course eat right: fruit and veggies, lean protein, lowfat dairy, good fats and whole grains.
And some red wine and chocolate!!
 
 
 

This is really a great thread! 
PurpleRules- How exciting that you iron your sheets!  Bravo!  I wish I had the patience for that.
My husband knocks me when I want to go to bed at 10 so I get 8 hours of sleep...but it really depends on how good a sleep I get.  If I wake up during the night because I'm hot I have a hard time falling back asleep....this has been the case the past few days here.  I don't know how my husband doesn't die of heat at night.  I have trained myself to go into the guest room that has no heat on to cool off and then go back to my own bed when I am not room temperature anymore.  And usually I have turned the heat off in our room already.  *sigh*
Also I sleep on my stomach with my face smushed up against the pillow and comforter.  I can't seem to find a gentle cleanser that doesn't really overdry my cheeks and forehead.  Paula's Choice has a nice one so I'll have to get some more.
I know I looked and felt better when I was running last fall.  I had extra energy to get me through the long 9 hour days at work.  I have been meaning to start again now that it is not pitch black in the morning.
-good sleep
-genlte face wash
-sunscreen
-water
-exercise

Cate: Have you tried Cetaphil? It's a GREAT cleanser if you have problems with dry skin. It's cheap, available almost anywhere, and dermatologists recommend it. But it might not get all your make-up off; at least, that's what I've found. That's why I do the two-step cleansing routine that's become popular. (DHC Cleansing Oil followed by Cetaphil)
 
 

I do get enthusiastic about some products, don't I? 
At least this one is cheap!

Fitness Brain,
There probably isn't scientific evidence on the satin pillows, but from my experience, I don't get pillow lines on the side of my face with I sleep on satin ones. I have also read this little tip in a few books.

pas: I can see how that would be frustrating. Cetaphil just isn't going to cut through make-up but its upside is that it really leaves skin dewy soft.

Retinol, as high a concentration as you can tolerate, limited short term use of cortisone or similar creams for wrinkles can be helpful but can have unwanted side effects, as of course can the retinoids. In addition always remember to moisturize prior to applying a pure retinol treatment on the skin and of course wear sunscreen that protects against both UVA and UVB rays and limit your sun exposure during the middle of the day as you all probably know.
Teddy
p.s. I am prescribed a prescription skin cleanser containing 3% benzoyl peroxide and a mild abrasive and find it highly effective for my combination skin. I always use it in conjunction with Cetaphil brand moisturizer, although I see nothing wrong with the Cetaphil brand skin cleanser formulated for oily skin (as opposed to the regular cleanser) for most individuals with combination or oily skin.
Teddy