What should I say in a Direct Message?

[The Beast Is Addie]

Well if it's a celebrity, sorry bruh, but that's probably not going to happen. Ever.
But if it's just some girl you know of, say: "Hey, my name is Luke. I don't really know you, but you seem really sweet and down to earth. I'd really love it if you'd talk to me sometime. I'd love to get to know you."
And that's about it. If she replies, she replies. If she doesn't, oh well! There's plenty of fish in the sea(:
--Addie<3

[neodanite]

Well, you definitely don't want to mention your age. If she thinks that you are a little bit older than she is, she is more likely to want you as a friend. As long as you don't want to date her, you are not likely to have your heart broken over this one. However, I think that, truth be told, you may have a little crush on her. Which is normal for your age.

I would keep the message very, very short. Just write something like, "Hey, I think you're cool and down to earth. I'd like to be your friend." If she ignores your request, well, she's 2,400 miles away and therefore it is no big loss. If she accepts you as a friend, congratulations! Just don't expect this to turn into a long-term romantic relationship. Cheer! : )