First, write a book. Write the kind of book that someone unrelated to you, who is not your friend, will want to read more than once. This book could be the kind of book that a perfect stranger will want to peddle and push and champion, and that other strangers will want to bind together, box up and send out into the world and that more people you don't even know will see and touch and carry around, and linger over. Maybe. Time will tell. At that point where you are not sure, but have hopes, hopes that have started to seem concrete and tangible, with details and tasks and dates, then, call someone who has several significant cameras and a love of literature and a fondness for you as well.
Next, think about what you love. Think about your favorite shoes, and what you like about the way you look. Brush your hair, which is gorgeous, and put on lipstick if you feel like it. While you are looking in the mirror to put on your favorite lipstick, notice that your eyelashes really are kinda long and you have that to be glad about. The things on your face that you like are the things that will make it easy to smile. Not a big forced grin, but the right kind of smile for a close-up, just a small thing, just a hint at contentedness. If you are dark brunette, with fair skin and deep brown eyes, it will not hurt to wear green. Or pink, or both together, or really, anything you know is good.
Now, think about outside. Think about the places where you once sat thinking about things you loved, or wearing that small smile, accidentally, without even really noticing it until you realized that someone you might have been in love with was seeing that smile on your face. Think about secret places, places that lend themselves to the extremes of human emotion, places where if you are not wearing the smile of the deeply content, you might be licking your wounds, having a safe cry. These are the places where you are likely to find a great blue heron, trees that have surrendered themselves to the water's edge, plenty of undisturbed moss, and probably teenagers smoking pot. All of that is fine. Pick your place, then stand there.
You do not have to think about smiling, or not smiling. Realize that no one is trying to make you look like anything other than yourself. Think about the things that made you write that book, good and bad, no doubt funny, maybe a little heartbreaking. Let a hint of it all show on your face. That's all anyone will be looking at.