Simplified steps:
1. Shoot in DNG
2. Develop in ACR
3. Get the white balance right (might sound counterintuitive for B/W, but this will help later on)
4. Convert to greyscale in ACR
5. Use the color sliders in ACR to get the "film tones" right. For a Tri-X look, drop the reds and greens a bit, but raise the yellows and orange levels. Other colors, adjust to taste.
6. Adjust whites and blacks to taste.
7. Open in Photoshop
8. Add grain and some character using Alien Skin Exposure
9. Final (and crucial) step: Add an Exposure adjustment level. Adjust Offset and Gamma. A very very slight offset will give it the scanned film look.
10. Enjoy!