There's a handful of things that make a difference, but a lot of aging is genetic and you can't change it.
Avoid UV light. That means no deliberate tanning, using sunscreen most days, covering up.
Maintain a healthy weight all your life. The older you get, the harder that will be.
Exercise for 30 minutes most days of the week. Light exercise is fine--a walk, some housework or yard work.
Eat healthy nearly all the time. Limit fats, processed foods, sugary treats, fried foods. Okay for special occasions only.
When and if you are prescribed medications, take them as directed. The fact that you feel the same whether you take your blood pressure or cholesterol meds or skip them doesn't mean you shouldn't take them.