How should I layout voltage regulators (VRs) to separate Analog and Digital?
Whether you separate the analog ground from the digital ground REALLY depends on how isolated the analog and digital functions are. 

If they are 100% separated, then running different grounds with them only connected together at the battery terminal connection is better.

If however, there are numerous control signals between the digital and analog circuits then the long current return path through a separated grounding system causes issues and a uniform grounding system is more appropriate.

If there are only a few interconnections, then careful layout and PCB design to have those circuits as close as possible to where the grounds separate may be sufficient to allow you to continue to separate them.  

Most of the time though, one really good ground plane is sufficient with the occasional localized ground "island" for a particularly delicate analog circuit.