Use a splitted ground plane to provide a separate analog and digital ground and route the individual grounds to a central ground star point, best near the voltage regulator(s). Take care that you use ground planes for the analog and digital sections, but, again, have them separated, by a gap.

The ground routing can look like in this example:



If you supply the analog and digital section by the same voltage, then filters are additionally needed to avoid digital currents from flowing across analog ground and unsanely increasing the noise there.

Kai