What is the best-practice for circular lego staircase construction? Aside from using the grey key-hole shapes, I'm looking for a Lego-standard or best-practice method for building a circular Lego staircase?

Requirements:
6-8 studs "wide" (from the center to outer edge)
Sturdy, play-able construction 
Connects at either 90 or 180 degrees to a floor.
There's a brick-built spiral staircase in the Pet Shop:



That's definitely the most common way to do it. You just build up around a central point. This can be expanded to use longer or wider steps:




http://www.mocpages.com/moc.php/267772

You can also use 2x2 turntables if you need more strength and/or larger stairs:


http://www.popscreen.com/v/6UIWz/Tutorial-Lego-Spiral-Staircase