Finalisation Guide
Before a cell can be considered "done", it needs to at minumum satisfy the following criteria. Please make sure you go through this list for any cell you are working on or reviewing before sending it off to the next stage.
General
If hammocks are placed anywhere in the cell, mark them as "ignored by sandbox" if no one is ever scheduled to actually sleep on them or swap them with a bedroll or other sleeping arrangement otherwise. They do not have functioning sleep animations.
Use the Cell View window to ensure every mesh in the dungeon is using a Skywind model and prefix (_) in the editor ID (Markers and effects are ok)
Interior matches the exterior, entrance matches exterior, load doors connected
Delete old dungeon layout if it still exists (Make sure you have markers turned on when you select the old layout, otherwise they won't be deleted with the rest of it)
Cell Data
Music - Make sure the cell has the correct music set. Dungeons have their own unique music tracks
Acoustic space - use the appropriately named one for that interior type size01 (or a more appropriate size, this will be the default for that cell)
Location - Need to make sure the interior has its own location, instead of using an exterior location. Also need to make sure the location has the correct keywords. For example Ondi's Shack in Khuul is _KhuulOndisShackLocation
Choose an appropriate lighting template with the prefix _LT_ (For example "_LT_InteriorImperialShop"). Check all the checkboxes under "Lighting Template" on the "Lighting" tab. This is so that the information gets inherited from the template.
Choose an appropriate image space ("_IS_InteriorGenericAncestralTomb" for example)
Make sure the owner NPC or faction is set, and if the area is a public place (such as a Temple) "Public Area" is checked.
Cells with sky lights/holes need "show sky" checked under the lighting tab and their proper region selected. Do NOT check "Use Sky Lighting"
Actors
Check the location's wiki page to ensure the right NPCs are present. Sometimes NPCs can be placed in an exterior, however. Just make sure they're nearby
For generic enemies like undead, Daedra, and creatures use the "1_DUN_" Actors. Estimate a difficulty tier 1-5 so that it's relative to the dungeon type, the region it's located in, importance/quest-related, and other factors. This will be fine tuned later.
Set the "Persistent Location" to the proper interior so AI packages function properly
For dungeons, have at least one NPC set as a Boss under "Location Ref Type". This makes it so an interior can be cleared. Often there is a quest with one of the enemies in the cell clearly indicated as the boss. Research the cell in the wiki to learn more about the context.
Place idle and patrol markers where appropriate. Ensure the proper NPCs are using them.
Set up proper NPC behavior packages and combat areas. More information can be found here.
Gameplay (Dungeons Only)
Approachable by all play styles (Lines of sight/cover for rogues, ranged fights, etc)
Ensure there are no pits or falls that the player can't get out of without relying on levitation
Ensure all traps are working and have proper scripts
Markers
Place a COCMarkerHeading at the main entrance next to the teleportation marker
Set up all environmental hazards. For example, every fire that the player can step in needs to burn them. Process: select your object, such as a campfire, click T (trigger) and select a hazard, such as 0LSC_HazardTriggerFireLight. A triggerbox appears; open its properties and assign its linked ref as the first object you selected. Resize the proportions of the triggerbox appropriately. Making it a sphere is helpful for stuff like campfires
Ensure NorthMarker is actually facing north
Sound effect markers - especially for things like waterfalls or Dwemer lights
Use Acoustic Space boxes for any part of the cell that isn't an appropriate size for its default acoustic space (Size 1 being small and size 3 being large). Use this with caution, as loops in the acoustic spaces fade out and back in even if they're the same interior type.
Use Combat trigger boxes to make sure enemies do not engage with the player earlier than intended.
For dungeons place sound and music cue triggers where appropriate ("Dread" before a final boss room, for example)
Lighting
Lights, 'dust beam' lights, and glow fills need their emittances set to the exterior (ex. "_FxBCSunlight" for dungeons in the Bitter Coast region)
If a cell has areas of vastly different size, or different tilesets being used (for instance an Ancestral Tomb or Daedric ruin that has a cave section) make sure the interior has had roombounds created for it. If not, either create roombounds or send it back to Optimization with a note that the interior will need roombounds. Set each roombound's Image Space and Lighting Template to the appropriate settings (ie, a Daedric ruin with a cave section would have the Daedric ruin segment roombounds set to the Daedric template, while the caves would be set to the region-appropriate cave template).
Note that if a roombound does not have an explicitly set Image Space or Lighting Template then it will default to what is set in the cell properties. So for the above example you could set a given Daedric ruin's cell to the Daedric Ruin template, and just set the cavern roombounds to the cave template.