title_body: How do you determine a New Letter's sound? I'm trying to create a new language, but I need some advice. How do you determine what a new letter sounds like? Is there a pattern, or do I just make it up?
upvoted_answer: If you're designing a fully new language, it's usually better to pick phonemes (sounds) before even thinking about orthography. Writing should really come after even grammar.
  If you're just designing a new writing system, then yeah, you just make it up.