How can I get a specific Floor in my Tower?

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.

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.