Interior signage is where accessibility requirements bite hardest, because they apply to ordinary door signs rather than anything exotic. The rules below reflect the 2010 ADA Standards for Accessible Design, and your local authority having jurisdiction is always the final word on any specific project.
Which signs actually need to be tactile
Signs identifying permanent rooms and spaces need raised characters and Braille. Restrooms, stairwells, exits, and numbered rooms fall into this group. Directional and informational signs, and anything naming something temporary, generally do not need tactile characters but still have visual legibility requirements.
Characters and Braille
Tactile characters must be raised, sans serif, uppercase, and accompanied by Grade 2 Braille positioned below the text. There are minimum and maximum character heights and specific spacing rules, all of which are set at fabrication and cannot be corrected afterwards.
Mounting position matters as much as the sign
Tactile signs are mounted on the latch side of the door, within a defined height band measured to the baseline of the characters, and positioned so someone can stand at the sign without a door swinging into them. A perfectly compliant sign fixed in the wrong place is not compliant.
Finish and contrast
Characters must contrast with their background and the finish must be non-glare. This is where a lot of otherwise attractive signage fails, because polished and mirrored finishes look excellent in a photograph and are specifically what the standard is trying to avoid.