I'm coming at this with a limited grasp of some European languages and for my world I'm faced with the daunting task of creating anywhere between 9 and 2000 languages (we never pick easy projects do we!?). They're nearly all for humans or at least humanoids.
So far most of the characters speak "common" with the odd phrase thrown around in the local tongue. Typically I sort of feel what a language should sound like (sing song, rough, playful, eloquent) type some random words (roughly matching the number of words of what I want them to say) and move on.
This isn't sustainable.
For starters I know I have no sort of dictionary for these languages, secondly I know I'm missing all sorts of rather important things like tenses.
Is there an established technique or procedure for creating, maintaining and developing a new language from scratch? What bullet point steps do the experts follow?