1. Separate analog and digital supplies and grounds. I believe you are already doing it.
2. Place separation between analog and digital blocks and fill it with ground cells. Substrate noise is also an issue that cannot be ignored. Because you are in research, be generous with that.
3. Large decoupling capacitors CLOSE to the blocks. By the way too much decoupling capacitors can also result in oscillations inside the chip. So its a good idea to de-Q the decoupling capacitors by using MOS transistors.