Professors are not always going to remind you of the test coming up next week or the fact that you must have something read by a certain date if you can expect to understand the lecture. Pay great attention to that syllabus given on the first day of class, visit your professor´s website and/or office to get any ambiguities cleared up, and learn to discipline yourself and organize your time to keep track of things.
Most professors are willing to give you some slack (unless they look and act militant or lack a sense of humor and basic facial expressions). Teacher assistants may not always be as compensating, but most professors will hear you out since they´ll be more willing to read a late paper than an illegible one made from a printer with only two drops of ink. But as usual, don´t abuse the privilege, and prove that you deserved that extenstion.
**Note: Always discuss a potentially late assignment with your instructor before it is late.
Once you find a professor who truly engages you, know to take classes by that professor in the future. The familiarity is a plus on both sides, and you are likely to learn even more and create a better rapport.
Get to know your professors BEFORE you fail an exam and want some kind of mercy. Drop by during their office hours, or e-mail them if they´re technically-inclined. A positive rapport always makes an impression on grading, however subconscious that may be.
Get to know your TAs as well as your professors, especially if your professors seem a little aloof. Teaching assistants can sometimes be your lifeline.
Take advantage of your instructors office hours. The one-on-one discussions will allow you to have questions answered that were unanswered in class.
The most important tip that I learned late in my university career was to research the professor as well as the course. Many universities have a lot of flexibility when it comes to electives or when you can take a course. Take the time to find out about who is teaching the course before you take the course and find out that the professor has difficulty with the language, hates undergraduates etc. Ask friends who have taken the course and also go to the student union office where they can often give you the information you need. if the professor has a bad reputation, drop the class and take it when it is taught by someone whom you will enjoy taking it with.
Talking to someone who´s had your professor before will give you little tidbits into that professor´s lecture style, and his/her´s favorite test format and focus.
From your friendly RN, that cares...