TLDR: We need to spice up the story before the player has a sexual encouter with a NPC

Mods in mind: primarily mods like Radiant Prostitution/Gigolo, Night Mistress Mansion, and similar... but in general any mod that adds flavor to the cold evenings ins Skyrim
Alternative mods: Sisterhood of Dibella, SL Eager NPCs,
Modders: Feel free to use this train of thought in your mods. Though I ask everybody to use this only in mods, that will be hosted here on LL and free to play.
For simplicity, I call the player the "host/hostess" and the NPC the "client".

LL prostitution-, brothel- and similar-mods cover a wide range of sexual encouters, sometimes inside the frame of quests. But mods do not always put great effort into the hard work to gain the client in the first place or they lack that part at all.
Simply spoken they look like 

1. Talk to client
2. win speech check
3. have sex

For my taste, this is a bit too simple and becomes repetetive. Thus it lacks variety and depth.
Furthermore, a complex setting will also benefit from a wide variety of non-sexual entertainment activities.
And not to be forgotten are some surrounding menial tasks necessary to make the encounter more pleasant/profitable.

I try to collect and describe these surrounding conditions, prerequisites and tasks in this blog topic. I hope that modders pick up as many of these ideas as they can and use them to spice up their mods.

I intend to edit & extend this posting when I stumple upon more ideas or find better ones.

The unseen tasks (just for completeness)
These tasks surely become boring on their own - so they should be optional if the player is interested .. or forced e.g. in a slavery mod

• stoking the fire, heating the house of sin
• buying and stockpiling the goods, food, wine, mead, clean sheets, new clothes and items,  ....
• keeping unwanted guests outside
• asking the wanted guests inside welcome the new client
• aquiring and arranging furniture and decoration

These tasks make only sense, if the story is focused on a special location with the right facilities. So far, I have only seen Night Mistress Mansion to use that direction

Menial tasks
Menial tasks or not directly part of the sexual encounters, but they may trigger encounters on their own.

•  preparing food & drinks
•  serving food & drinks
•  cleaning clothes and dishes
•  cleaning rooms / tidying beds
•  arranging the place of sin, e.g. placing pillows, tasty food, fruits, wine, mead, towels at convenient places

They should either be part of the surrounding activies, give buffs to please the client or simply offer their own stream for the player
We can find some of these already in Night Mistress Mansion or Radiant Prostitution.

Appearal
To have success the host needs to have the proper appearance.

•  clothing
•  jewellry
•  scent, perfume (magical effect?)
•  be clean (Bathing in Skyrim?)
• illusion spells, alteration spells

These should have buff/debuff effects on the chance to gain a client, to please the client (quest success) or to gain a bonus tip.
Or, in the hardcore variant they enable/disable the clients attention at all

Manners & ettiquette

•  skill in speeach is the obvious one
•  ...but there should be more ...

Maybe this needs its own skill tree with perks? Or maybe something similar like https://www.loverslab.com/blogs/entry/6355-think-tank-the-learning-curve-for-prostitution-mods/
   
Alluring and entertaining tasks
These tasks belong already into the erotic arts. They aim to win the clients heart and make him susceptible for further sexual encounters... or make him to spend more money

•  plain bard tasks like singing, playing instruments or reciting pleasant literature
•      -> Bard mods could be handy for this
•  enticing the client to buy more drinks
•  drinking games - make the client drink more, secretly ditch own drink to stay sober
•  drinking games - striptease games
•  dancing (e.g.like in TDF's prostitution mod)
•  word games - solving some riddles, it ends in a striptease anyway
•  ... to be continued ...

Semi-sexual entertainment
These activities are in the grey zone, between the non-sexual and sexual part.

•  hide and seek game (DD/Zap Blindfold)
•  touch and guess game (DD/ZAP Blindfold)
•  try and guess game - SL foreplay animation (DD/ZAP Blindfold)
•  escape games (escapable Devious devices)
•  theater play / sex show in front of the audience
•  ... to be continued ...

Who could use all this?

• obviously every prostitution mod could use them
• every brothel or other similar etablissement could use them
• mods around Dibella and her worshipping
• to a lesser degree also Mara
• every mod focused on seduction
• Sanguine related mods
• mods with inns, bathhouses, casinos and other locations .... even if sex is not their focus
• slavery mods with a dedicated location, as long as the player has at least some limited freedom

Some references

NNM by @Delzaron https://www.loverslab.com/files/file/3831-night-mistress-mansion/
RP/G by @-Caden- https://www.loverslab.com/files/file/5392-radiant-prostitutiongigolo/

TSD by @DeepBlueFrog https://www.loverslab.com/files/file/392-t

SL PAP by @TheDriedFinger https://www.loverslab.com/files/file/403-p

SLEN by @BeamerMiasma https://www.loverslab.com/files/file/2182-sexlab-eager-npcs

Jobs of Skyrim by LittleOrk https://www.nexusmods.com/skyrim/mods/25020/