I love tuxedo shirts but have no idea how to wear one and still look feminine. Any suggestions?
Join the club. (And if a club doesn't exist, let's start one!) My first suggestion: Let's stop associating tuxedo shirts with masculinity. (I assume you don't plan on wearing yours with a bow tie and dress suit, right?) After all, once you remove the shirt from its tuxedo context, you're just left with, well, a shirt. (I'd say your bigger concern is wearing one without looking like a waiter at a Michelin-starred restaurant.)
It will be tempting, of course, to pair the shirt with black pants, but know that the best style statements result from bold juxtapositions. For instance, try wearing your shirt with jeans – either crisp and indigo or faded and frayed – plus a pair of classic pumps. For a more polished look, you might consider a pencil skirt in grey or navy.
A plaid pant would also make a dashing statement. Yes, I'm using "dashing" to describe a feminine look. Let's acknowledge once and for all that fashion today is fluid. And fun. Even when it's formal.