The funny part about your post is that you're worried about how to decide what shirt to pick. Wu Wei means just picking a shirt. ^^ To me, wu wei is efortlessness. It doesn't mean you just plow through life without looking, bouncing off things. It means you don't worry about what you're doing. You'll pick the right shirt if you trust yourself enough to pick a shirt. Even more, if you don't have any intentions or desires, any results are a success. So, wu wei is also the outcome of removing your stake in the world. You win the lottery, good. You lose your house, also good.
You can make choices, but they don't come from desires, they come from practicality. When you're hungry, eat. When you're tired, sleep. When it's time to put on a shirt, you'll know what to do.