Portrait photographer's know that a subject's eyes are what's most important in a photograph. Everything else is secondary. We're naturally drawn to people's eyes, so if the eyes are out of focus or they don't sparkle with reflections (called "catch lights"), the image won't keep our attention for very long.
Take Madison's photo (above): Her eyes are sharp, they're "posed" to tell a story, and they sparkle with reflections.
If you're a high-school senior, I'd love to do your senior portraits! All you (or one of your parents) have to do is call or write and I'll walk you through all the details!