Diane Keaton is the epitome of style. She makes popped collars, conservative turtlenecks and classic blazers look chic in a kooky, on-trend way, but it turns out there may be another reason for her covered-up style: Keaton is a skin cancer survivor. Diagnosed with basal cell carcinoma at age 21, Keaton has had numerous run-ins with skin cancer, making her a hat-wearing, sunscreen-toting advocate for sun care. We recently sat down with her at a L'Oréal and Melanoma Research Alliance event, and here's what she had to say about the sunscreen she keeps in her pocket, how she picks her clothes and her secret beauty weapon.

What's your best beauty advice?
Wear sunscreen. You've got to put it on. Six years ago I had a squamous cell, which is serious. And I had it for a very, very long time [before it was diagnosed]. I knew something was up, but no one could find it. I had three biopsies before they found it. And it was deep. A squamous cell cancer is second to melanoma, and you can die from it, because it will spread. It's really not a joke. If you're going to doing something for your beauty, you've got to take care of your life first.

How do you know when to get something checked out?
Look, I've been around. I've had so many basal cells I knew something tricky was going on. But they kept taking the biopsies and saying it's probably something else. And that's why cancer is tricky. It's evil. You can't always catch it with a biopsy.

What is your favorite sunscreen?
I like thin sunscreen. When it's humid I especially like something sheer. I keep L'Oréal Silky Sheer BB Face Lotion SPF 50 in my pocket.

What's your secret beauty weapon?
Stick-on nail decals. They're not appreciated enough. They last for two weeks, no problem-o.

Finish this sentence: You're never fully dressed without a ...
Hat, duh. And gloves, long-sleeved shirts, turtlenecks, the color black, high-heeled boots ... it's endless. The best thing in the world is selecting what you're going to wear. It's fun, it's creative and it's full of life and energy. I love it. Plaids, you can put some plaids in there. I like scarves, I like ties.... Look, I like it all. I like everything about clothing.

How did you develop your iconic style?
I like what I like. I put on what looks good on me. I think that's what everyone should do. I think everyone should be individual and find what they love.