I've never taken a creative writing course in school before, but here are some things that I picked up that should help you out when you're trying to write a scene.
When you want to write an emotional scene, find some music online that fits the mood of that scene. Happy music for happy/funny scenes, depressing music for depressing scenes, dramatic music for dramatic scenes, you get the point.
Secondly, when you're stuck with what to say in a dialogue, act it out yourself. Stand up (hopefully nobody's around because that would be embarrassing.), maybe listen to the fitting music along with it, and start acting out the scene and let the dialogue flow through your mind, imagine yourself in the scene and feeling what they feel, and what you say in the scene is what you should write down for their dialogue. It doesn't HAVE to be what would be said in the dialogue, but remember what you acted out and write it as notes for the scene, at least.
P.S: Where do the advanced MMD'rs find their model parts?
's OCs always look SOOOOOOO amazing, I just wonder where they find the things they use~. Obviously most of the results are probably because they are talented PMD/X Editors, but still~.