Branching stories are simple sims where players make a series of decisions to shape and advance a story. I have found ten surprisingly easy and effective "little" techniques to make them much richer.
Here is the tenth and final.
Every time a player fails, make sure he or she understands very thoroughly why the path was wrong.
Specifically, when a player arrives at a negative outcome, show the player both the immediate, apparent, and high-probability consequences (which are often positive) of the traditional behavior, but also the long term, hidden, and/or "unlikely" but possible consequences (which can be devastating). Allow the player to experience emotionally the direct negative consequences. Visualize the "invisible system," which is the flow of events that people can't normally see, but leads to problems.
For example, consider a cyber-security sim.
Do not just say, You fail. Putting the thumb drive in the computer is a violation of IA Policy 17543b.
Instead say, Unknown to you, the thumb drive had been infected with a worm during the manufacturing process that had not yet been identified by a major anti-virus company. When any thumb drive is put into a USB port, it auto-runs a small program. This time, the virus was able to infect the local computer, and then, two days later, the server. Within a week, the virus had spread to not just local computers but remote computers as well. A group of mobsters in a foreign country was able to access passwords and then other mission critical information, which they sold for two thousand dollars to a foreign government. The mobsters used this money to bribe officials to get a ton of heroin into the United States, and the foreign government began to access pieces of proprietary intellectual property which they passed onto competing companies.
Then, of course, allow the player to try again. (This means the sims have to be short enough to encourage replay.)
Players should never make the same mistake twice, if a sim is deigned well. In fact, the player should leave the sim being a rabid supporter of any relevant rules. This is how branching stories can build true conviction.
Examples of real screenshots can be found in my portfolio. While this portfolio necessarily does not include client confidential work, it nonetheless gives a good sense of simple and straightforward projects.