"How are you?"

That question, when asked in a genuine manner, speaks a lot. When you say it genuinely, you are expressing your concern about someone, wondering how has their day really been and whether they've been okay or not. You want to know everything that's been going on in their life from the last time you've seen them, be it a day or even an hour ago. You want them to know that you're there as a shoulder, as their rock. You're saying: "I'll be here, dump it all on me."

But most of all, you're letting them know that they have been on your mind. The whole time.