MAPPING FOR HERETIC

-No jumping or crouching can be used by player, so don't map for it
-FLTSLUD1 liquid flood is generally expected to be damaging
-false walls can be used (wall that looks solid but can be walked through), ideally used sparingly
-Generally Use SW2OFF for your exit switch texture
-Wings of Wrath (flying item): Make sure if you let a player fly to an area they would not be able to escape without flying, provide at least a teleport exit in case their wings wear off while in that area. Another wings of wrath could be included in the area as well.
-Plenty of 16, 24 and 32 wide pillars
-Heretic mappers not afraid to work on diagonals, usually on snap 8, pillars often 22.3 wide (shown as 23 while dragging vertex)
-not afraid to have dark areas, sometimes as low as 96 brightness

Buildings
-buildings generally constructed in snap 16 and 8, with diagonal corridors with stairs often snap 8.
-doors generally 64 wide, either 8 or 16 thick, with 8 or 16 wide strip either side.
-small door building: 8 thick, with 8 thick strip either side
-larger indoor building: 16 thick, with 24 thick strip either side
-buildings generally with 24 or 16 thick walls. 24 to accomodate 8 thickness door with a strip of 8 thickness each side
-interior rooms generally 88 - 128 high
-Building floors generally 8 higher than ground level and FLOOR10 texture
-corridors generally 64 wide, sometimes as tight as 48
-Exterior small windows: lower section generally 32 above ground level (4 scrolls with mousewheel), window sector generally 32 high

Buildings usually with multiple vertical levels, sometimes as simple as a stairway around the outside of a central room, giving the impression of height and multiple levels, sometimes much more complex.

Reference map to check out: E1M5 - great buildings