In college, I learned very abruptly that my planner is my best friend. It allows me to keep track of exams and allows me to give myself enough time to study. At the beginning of the semester, professors hand out the bible to the course: the syllabus. Tucked between the section on not cheating and when their office hours are lies the most important part. The test dates. The instant that syllabus is sent out, the dates are already in my planner.
From that point, it is generally cruising in that class with homework and small assignments until you flip the page in the planner again and see the word Test, which makes your heart pound just a little faster. I have found that giving myself one week to study is the best way for me to study (generally). I understand that every single day of that week may not be spent studying, but even thinking about the material makes me feel more confident about it.
As the test creeps closer and closer the professor may send out a study guide or practice problems. PLEASE USE THEM. They are there to help you and often mirror what is going be on the exam, at least in part. Being familiar with the type of question to expect may make you more confident going into the exam because you will not be taken by surprise when the test is all written problems and you were expecting multiple-choice or something like that.
On the day of that test, remember the tips your mom gave you in elementary school before the standardized tests. Eat a good breakfast and get a good night sleep. If you are sitting in the test with your stomach grumbling every 2 seconds, it makes it very hard to concentrate on the test that is sitting in front of you. Similarly, if you show up as a zombie because you have pulled an all-nighter, you will barely be able to read the words that would be simple to you otherwise.
I'm sorry for this long rant about tests, but I have several of them coming up and I really just needed to remind myself of these things.