Geofiction 101: Creating Languages
Constructed languages - or conlanguages - have long been a staple of geofiction, ever since J.R.R. Tolkien created the Elvish tongue, or H.P. Lovecraft came up with the confusing language his Great Old Ones. Language and communication are essential elements of any sentient race, so having your creations speak a language of their own goes a long way in making them seem more realistic.
Of course, any civilization you create could just speak English (or your native tongue). While that is acceptable and very common, though, some prefer the challenge of coming up with a language of their own. I must stress that this is one of the more difficult tasks in geofiction, but there is advice out there to make it a bit easier.
(As a bit of motivation, creating a language was the prime driving force behind why Tolkien created Middle-Earth. He wanted to create a beautiful language and needed characters to speak it!)
The Simplest Method: Word Substitution
If you ever created a make-believe language as a kid, then you probably just used simple word substitution. This is where you take a language and just create words to replace the real words, leaving the underlying grammatical structure intact. This has the benefit of being very easy to create, since all you are doing is coming up with a new way to arrange letters. You can even go one step further and create your own alphabet and do a direct letter by letter substitution.
The downside to this is that this language is difficult to actually speak, since coming up with new sentences requires one to memorize many root words and conjugations. That isn't to say you couldn't communicate with it, but true fluency is dependent on understanding grammar and syntax in addition to words themselves. Still, this is the most popular method used to create conlanguage.
Spanish is often viewed as one of the easiest languages in the world to learn. In fact, it is quite easier to pick up than English - which is viewed across the globe as somewhat difficult to master compared to other languages. Spanish uses a relatively simple sentence structure with easy-to-understand conjugation and basic patterns. Indeed, the world's most popular conlanguage, Esperanto, borrows heavily from Spanish.
Using word substitution in conjunction with adopting Spanish grammar and syntax is a good way to create a workable language for your creations.
Creating a Language from the Ground Up
This is arguably the most difficult method: creating a language - words, grammar, syntax, and sentence structure - from the ground up. You have to not only create a dictionary of words - you have to also create a system of conjugating them and incorporating them into a grammatical structure. This represents an enticing challenge, though, which is why many choose this method.
Studying Esperanto and Quenya, Tolkien's language of the Elves, can actually help quite a bit with crafting your own language, if you are interested in pursuing the concept further.