I'd like to point out that Hermione stopped smiling 1 year before Harry and Ron did. She probably knew the danger long before them <--- I'd like to point out that Harry stopped smiling after year two and Hermoine smiled year three.
"Excuse me? Could you tell me how to, uh." "How to get onto the platform? Its Ron's first time to Hogwarts, too. All you have to do is walk straight at the wall. Best to do it at a bit of a run if you're nervous.