Use a grainy film. I'd try Delta 3200 for a huge wash of grain (actually an ISO 1000 film, so bear that in mind when re-rating it) or HP5 for a sharper grain that appears to be a part of the objects in the frame, as opposed to a wash of grain over the image. Overexpose the heck out of your film – at least three stops, and the more the better, until the point where you lose too much contrast. Process for a long time in a developer with a low concentration of silver solvent. You can get long times by diluting developer. You can also get low concentrations of silver solvent by dilution, and/or the use of Rodinal. You can also use hot developer, temperature changes, and/or excessive agitation to purposefully mess up your emulsion. Print high contrast prints to accentuate sharp grain to its fullest. Print low contrast prints for the washed over look. You can also lith print if you don't mind the hues and tonality you get.
IME HP5 is much grainier than new Tri-X; the Tri-X is amazingly soft-grained now, despite its reputation for grain. It's been pretty hard for me to screw it up purpose, so I use those two films I mentioned instead. I can get excessive grain from HP5 simly by using HC-110 dilution H as opposed to dilution B.