In "The Shop Around the Corner" where did Margaret Sullivan's
character agree to meet Jimmy Stewart's character and how was he to
know who she was?

Hello.

Jimmy Stewart's character (Alfred) and Margaret Sullavan's character
(Klara) agree to meet in a cafe.

He was to know who she was because she'd have a red carnation and a
copy of the book, "Anna Karenina."


sources:


" Sullavan goes forth to meet her blind date carrying a carnation and
a copy of Anna Karenina, and the cafe encounter that follows between
her and Stewart is one of the most beautifully choreographed set
pieces in the history of romantic comedy, rife with cruelty, kindness,
comic misunderstanding, literary allusion, and the desperate pride of
two lonely people."
http://www.seattleweekly.com/film/9850/film-taylor.php


From the script of "The Shop Around the Corner":

"I'm meeting her tonight,  :   in a cafe.     
- A red carnation?
- Yeah.
Yeah.
She's using one for a bookmark in a copy of Tolstoy's Anna Karenina."
http://www.script-o-rama.com/movie_scripts/s/shop-around-the-corner-script.html

-----
search strategy:
"shop around the corner" meet "jimmy stewart"
"shop around the corner" "a carnation"

I hope this helps.

Thank you.