Here are the general script steps:
* Fill Basins
* Shrink the continental shelves slightly
* Smooth Prescale Offset
* Incise Flow the entire world
* Fill Basins
* Smooth Offset
* Select all terrain <40 degrees F
* Incise flow just the selected area, to try and replicate glaciation
* Lower rainfall around the horse latitudes by 20", and raise the avg temp by 10 degrees
* Raise the rainfall elsewhere by 20"
* Select all landmasses, drop rainfall by 1" per 10 pixels in.

Pretty much none of these are new - I've discussed them elsewhere in the forums. I'm putting them all into a single project to see how realistic they are and if there's anything more I can add to it.