Two NaNo's ago, I went and created a language. I borrowed books on linguistics from the library, read about all the different structures of sentences, all the different sounds, and my brain exploded. It was all way to much information, and the remnants of my brain wouldn't heal all day, despite all my hot chocolates (and looks from fellow Wrimos).
I have no idea how Tolkien did it. Gah. I bow many times in his direction.
But, I discovered, it's really simple to fake a language. We use a lot of smoke and mirrors in writing, to make people think we know what we're talking about (really, what do I know about collecting souls? or living in the time of the Black Plague? Not a thing) and it's not different with languages.
- Keep the sounds consistent. German has a lot of guttural sounds, Bushmen have clicks. Maybe your made up language revolves around A and lots of apostrophes. Just makes sure all the words you make up sound like they come from the same place.
- Use words in your writing. Refer to a type of tree by the language, use a word as an insult, an idea.
- Have language be tied to culture. Have a suffix to a name indicate gender, a have common phrase be tied to a way of thinking (aka 'I see you' from Avatar), show there's purpose to the language, other than to name things.
You might also want to keep a dictionary of words you make up. I find it's helpful for consistency of sounds, and to make sure I don't call something by two different names.
Today's bit of Twisting Tongue:
Lolly Linguine laments lying.
(Just realized it's Friday the 13th! Ahh!)