In the case of my latest story (
It's Good to be the King), the initial idea came from the concept of
prima nocta - the law which once existed in parts of England and Europe which said that the Lord had the "right" to sexual relations with any of the women who lived on his lands, whether they were married to someone else or not. Those who have seen
Braveheart will be familiar with this.
Of course this "right" as practiced in real life amounted to legalized rape. But it got me to thinking... I could write a story about a King who was so popular with his subjects that the women
willingly offered themselves to him, by the dozens. I invented a fictional, rather idealistic kingdom where people had come from all over the world to settle, so that I could have characters of many different races and cultures, and the King himself is a former commoner to make him easier for the reader to relate to. I decided that the King would be seeking a Queen, in order to provide another reason why women might throw themselves at him, and I've set the story during a time of festival and celebration to bring in visitors from distant lands and so that the people might be in a "partying" mood.
I started thinking of the different kinds of women who might live there and be potential sex partners, and settings which would facilitate such things. Of course the King could have a mistress, and servants. A tavern wench was another obvious choice, and there could be a whorehouse in town (which I later changed to a public bath, so it would be more appropriate for the King to visit). My main inspiration for the women themselves came from
Baremaidens.com, a soft-porn website with a fantasy/medieval theme; I would decide on a basic character type (for example, the thief in the woods), and search through pictures until finding a good fit; I then looked through other pictures of the same model to see what storylines could be generated, and what kind of personality one could surmise from the general look. Sometimes, it was the *lack* of suitable pictures which led the story in certain directions; for example, I had my heart set on using Charlotte Stokely as my model for a character who I wanted to introduce frolicking in a meadow, but I couldn't find a suitable picture of that (it's surprisingly hard to find nude photos which are not too modern - something as simple as tan lines will spoil the illusion!). I did, however, find a set of Charlotte naked by a stream, so the story has the King stumbling across her having a bath - which actually sets up a good "choice" whereby he can hide and watch, come out and try to join her, or just decide to meet her later on.
I wrote the introduction, six initial options, and a "Meet the Characters" thread before posting anything (I usually do this so that I can establish a strong "trunk" for the story to branch off from), and I found that potential storylines simply occurred to me as I was writing them. I have very few plans as to how to continue on the different threads; for the most part, I'm just seeing where they lead, and in fact I find that planning too far in advance tends to slow me down. The writing itself is a greater inspiration than just about anything else... once I get started, the ideas just come swimming in, and the great thing about CHYOA is that one can explore ALL the different ideas instead of having to narrow it down.