The #1 piece of advice is to determine what the assignment is and focus on the assignment. You can be an exemplary writer on a technical level and contribute high quality content but if it does not address the assignment, you may be looking at a B paper rather than an A.
Determine which of the following your assignment is and write accordingly:
If it’s a persuasion paper, pick a thesis, focus on it and fully support it. Find evidence to back your points and go all out. Don’t muddle yourself weighing the pros and cons. If it’s supposed to be a balanced or neutral paper, present viewpoints on both sides or leave opinions out of it.
If it’s analysis, you express your own observations and opinions because the professor wants to assess your capability of forming your own opinions. If it’s a research paper, your analysis carries no significance unless it is supported by a credible source.
If the assignment regards a work of literature (i.e. plot, devices, characters), be sure to stay focused on the literary aspect of it. While some context is helpful, don’t spend too many sentences discussing the time period or author’s life if its not the focus on the paper; When describing characters/authors/notable people, only describe them insofar as their relevance to the paper.