|The Star Wars Allphabet|
Those of us in the Western world, especially in the western hemisphere, find it easy to take for granted the fact that we (typically) use the Latin alphabet. The Oxford dictionary defines the alphabet as "a set of letters or symbols in a fixed order used to represent the basic set of speech sounds of a language..."
However, there are many other alphabets in the world, such as the Cyrillic (which Russian uses), Greek, or Arabic alphabets. Some don't include vowels, such as Hebrew and Arabic, in which case, they are referred to as "abjads".
Most alphabets we would think of are considered linear, meaning that they are designed to be written on paper. However, there are non-linear systems in existence, such as Braille.
If your characters are literate, launch some confusion upon them by introducing some different alphabets. Have different writing systems used in different parts of the country, or have them travel to a foreign country where they can speak, but not write.
Consider the number of letters in an alphabet and how that might affect electronics and their practicality for your characters to use them. How has technology influenced the style of writing? Carved letters might tend to be blockier, while handwritten letters might be smoother in nature. Do the machines in your story that read writing need a certain type of script to be able to identify letters? How does the number of letters in your alphabet affect spelling, contractions, or signage for the story?
Really, the possibilities are endless. Enjoy thinking up some ways for writing and alphabets to play into your characters' lives!