2. Bring her flowers
He manages to find out that her favorite flowers are peonies, and runs out immediately to buy a beautiful bouquet of the flowers in every color imaginable. He hopes that it doesn't seem too stalkerish that he knows her address, and that she isn't home, and that he's got her favorite flowers.
He delivers them with a card that says "From your secret admirer" and leaves before she gets home. Of course, he hides behind a corner in the hallway and watches her come back and find the flowers. She smiles.
The next day, he's at the university to ask Miles something (and of course he isn't hoping for a chance to see her. Ahem.) and when he's leaving, he spots her talking to a guy.
He's about to go over there and say hi when she says something that stops him in his tracks.
"So were the peonies from you, Justin?"
Arthur refrains from blurting out, "No, they're from me, and I love you. A lot."
Justin looks confused for a brief second before saying, "Um, yeah!"
Arthur wants to go die in a hole when he sees her smile at Justin.
The next day, she announces that she can't stay too late because she has to get ready for a dinner date with a guy named Justin who gave her peonies and isn't that so sweet?
Arthur smiles the fakest smile he has ever smiled and when he looks up, Eames is looking at him with a knowing look on his face.
Arthur glares at him and goes back to work, and he's just about to hack the mark's email account when a paper airplane flies onto his desk.
That awkward moment when a girl thinks that your gift is from someone else and goes out for dinner with that someone else.
Arthur cannot help but agree, and as he watches Ariadne leave to get ready, he sighs and wishes that he'd signed the freaking card.