Unfortunately, there's nothing you can do to postpone aging -- it's a natural process that begins the day you are born.
But, the good news is, you can take steps to lessen the affects of aging through your lifestyle.
My motto is, "everything in moderation." Eat a healthy diet but don't deny yourself the things you like -- just balance them out. Also, try not to eat too many processed foods. Even if you don't have the time to cook a meal everyday, try to take advantage of supermarkets that make up meals so you're not living on fast food.
Exercise regularly -- if you don't have a lot of time, at least choose the stairs over the elevator or park further away from where you're going so you get a few more steps in.
Find ways to destress -- read, take a walk/run, play with the kids, take a sunday afternoon nap! Find things that are relaxing and fun to do. Believe it or not, stress can shorten your life and also cause a myriad of health problems.
Get health check-ups appropriate for your age and be proactive in your healthcare. A lot of health problems are diet related.
I hope this helps you. If you need more info, just ask!