How to create a Pen and Paper RPG

Creating a successful pen and paper roleplaying world requires both an understanding of mathematics and literature.

In order for a developer to create their own roleplaying game, they first need an idea of what they are wanting to do. Typically, it's a good idea to define the concept in the title of the world that is being created. Some examples include Dungeons and Dragons, World of Darkness, and Shadowrun. Each of these names catches the eye of the reader, and defines what it is that the setting is in the most general way. Once a concept has been made, the developer needs to define how complicated or simplistic they want the game to be.
There are three main types of roleplaying game dice systems that are in circulation with popular pen and paper RPGs today: there is the D10 system, the D20 system, and the D100 system. The D10 system uses a number of ten sided dice equal to the trait pool, defined as the player characters raw capability, to determine whether or not a certain action succeeded or not. If the dice roll above a targeted number of the ten sided dice, then the number of 'successes' define how well the action taken performed. The D20 system actually involves a use of all dice, for various different traits in various different circumstances. Meanwhile, the D100 system is a percentiles game, where you have a certain percentage chance to perform something and when you roll, you need to roll under the percentile required to succeed. Each system employs a number of mathematical formulas players will use to exploit a system, and game developers need to define whether they want a simplistic quick and dirty game, as defined in a D10 system, an advanced complicated system, as defined in the D20, or a mix of both options as defined in a D100.
Once the developer has decided what mathematic system they want to use, its best to define what kind of setting will be within it. This hopefully has been started with the title, but it’s at this point they need to embellish; randomly creating a scenario is not enough. People do not get attached to things that are unfamiliar to them; it needs some ground in reality, which people can visualize and connect with that world. This means that the developer needs to research either history, mythology, or bits of science, depending on the setting of the game in question. In practice, youth enjoys things of the imagination, but age enjoys things to which can be connected and corresponded with.
Finally, once all these things have been established, the developer needs to write a story for the setting. Even when the developer is not creating the major characters, they still need to write a story for the world which they are making the game for. The reason for this is to give the game a ground to stand on. Dungeons and Dragons, World of Darkness, Shadowrun - all of these games have stories for their world from which the characters are born from, and it's those stories which truly define the game itself. Perhaps most importantly, beyond both the knowledge of literature and mathematics, a RPG developer needs imagination. George Bernard Shaw once said, “Imagination is the beginning of creation. You imagine what you desire, you will what you imagine, and at last you create what you will.” While a developer needs mathematics to create a good system for a roleplaying game, and they need a knowledge of literacy to create a setting which people can connect to and envision, they need imagination in order to do anything at all. Imagination is where they start. It leads them to the end: to a work of art which is enjoyable to anyone who plays.

References
Shaw, G. (n.d.). George Bernard Shaw Quotes. Retrieved February 26, 2015, from http://www.brainyquote.com/quotes/authors/g/george_bernard_shaw.html Gygax, G., & Arneson, D. A. (1974). Dungeons & dragons. Lake Geneva, WI: Tactical Studies
Rules.

The world of darkness: Storytelling system rulebook. (2004). Clarkston, Ga.: White Wolf Game
Studio.

Shadowrun (5th ed.). (2007). Catalyst Game Labs.