Good writing is clear writing. To be clear, you need to know the purpose of the writing assignment.

Like audience, purpose in a university setting is problematic.  For most of us, we write in order to get good grades.

While that is a sort of purpose, it is not a purpose that will help us write clearly and communicate effectively.

Here are some purposes that will help us write clearly:

to inform

to show understanding

to persuade

to show results

to entertain

to analyze

Instructors will communicate the purpose of the writing assignment explicitedly, implicitedly, or not at all. Regardless, it is up to you to write with a purpose fully in mind. 

Some writing has more than one purpose; decide the main purpose, and then all other purposes should serve that purpose.

Know your purpose and write with purpose.