I pick out options. I'll give DD the choice of shorts, skirt or dress. Then from there she picks from 3. I tell her if she doesn't choose in my timeframe, I choose and that's the end of it. So if she wants a choice, she better pick. You can set a timer for this activity. I also try to lighten the mood by doing stupid things like saying, "So these socks here, they go on your ears, right?" and DD will say, "No, silly! They're for feet!" and I'll say, "Oh, I don't know about that. Are they feet shaped? Let's see...why they are!" My DD is also slow to wake, so I talk to her about her options over breakfast and then she gets dressed just before we go.
Which is not to say that there aren't mornings when I just pick the things she needs to wear and we go anyway, even if she cries, but it seems to help to offer limited, directed choices.
Just today she asked for her bunny socks. Guess what pair of socks is MIA? So I got out other socks and said she could choose frogs or ladybugs or pandas, but we'd have to look for bunnies when we came home. She grumpily chose the pandas after I reminded her that she chose or I did and by the time we put shoes on to skip out the door, she was fine with the pandas. Kids....drive you crazy.
And FWIW, our preschool says basically make sure they are dressed for the weather but if they come to school in a tutu and superhero cape and pjs, nobody cares. Sometimes it's not worth the fight.