The easiest way to get extremely fine grain is simply via film choice. The next easiest option is negative size.
Perception can also effect grain.
The more contrast an image has, the more grain appears. A printing paper's surface can influence grain perception. The less glossy or more mottled the surface, the softer looking the grain. Poor sharpness of the final print due to poor optics or poor focus can reduce the perception of grain. Sometimes this is done on purpose.