Well some general was to slow aging is by:
staying out of the sun
using a sunscreen moisturizer everyday
wash your face with warm NOT hot water
use a good hydrating cream every night.
except for that..you'll soon find that time marches on and eventually you'll find it marching across your face.
I am a man. I hope this does not offend you at all but in my view you will age no matter what you do. you may be able to shadow that physical aging but both mentally and physically you will age.
eating right and excersing keep you looking young. lifting weights releases hormones that keep you young but since your a girl you probably wouldnt want to lift weights but excersise
Eat healthy, don't smoke, don't drink excessively, exercise in ways that maximize health benefits without hurting your joints, get a tempurpedic mattress so you get a better sleep... and be happy. Spend your time with people who don't stress you out.
Don't smoke or use street drugs. Avoid sunbathing and use sunscreen if you have to go outside. Get enough sleep (8 hours). Don't get too fat (you don't have to be a bikini model, but obese ppl do look older). Eat plenty of fresh fruits and veggies. Avoid really stressful jobs.