Unless you're writing something very formal, try to write how you talk. Don't try to sound smart by using unnatural vocabulary or elaborate phrasing - you're more likely to trip yourself up. Also, don't try to copy other writers' style; you want to stand out, not be indistinguishable from the crowd.
You can always tell when somebody probably just has a thesaurus open when they write >.> But the same advice goes the other way. Write how you talk and you likely won't write badly
I have worked with a fair number of writers who you can talk to all day and they can clearly articulate their points, but the moment you ask them to put it in text they overthink it and try to impress the professor. The result is all but unintelligible.