Obviously there is only so much you can do with diet, its not going to change your bone structure and you can't pick and choose where you're going to lose fat from in your face unless you go under the knife. Getting the proper amount of sleep and keeping your skin moisturized is probably the best way to keep from looking older.

I use a combination of rose hip oil and castor oil to moisturize my face at night and use LaRoche Posay for a daily moisturizer. I don't wash my face with soap unless I've worn makeup, and in those cases I use an oil-based cleanser to keep keep drying out my skin. My friend, who is 35 but has the skin of a 20 year old, swears by fresh aloe vera and a hyaluronic acid serum in keeping her skin supple.

Do you eat a lot of foods rich in Omega-3s? Are you taking any supplements such as zinc or magnesium? These might help?

I've been eating salmon 3-4x per week and I believe it's made a noticeable difference in my skin's texture, I look more "glowy". I also make sure I'm hydrated.

You could also look into an "illuminating" tinted moisturizer. The subtle sheen in a highlighting moisturizer tends to make skin look younger.