I really really want a specific floor (Glass Studio) in my Tiny Tower. How does the game decide which exact business will go into the "Creative" floor? Do I have to meet requirements (such as tower height) to unlock certain floors?
The floors are completely random. There is no way to make sure you get a certain floor in a particular category. You just have to wait and hope it shows up when you build.
With the recent release of version 2.0 (July 26, 2012 for iOS devices), you can pay Tower Bux to build a specific floor from all of the not-yet-built floors.
You can't do this while a floor is under construction. Once you have built an empty floor (using coins), you tap on the floor and choose "Choose Specific Floor" from below all of the "Random [Floor type]" buttons.