When your teacher says, "study for your test Friday," what exactly does he mean? It's a bit ambiguous, and many students do nothing at all. This lack of studying typically does not result in good grades. (There are, however, those few students who do not study and still earn a 100).
The most basic form of studying is memorization. One will only find this on spelling tests.
More than likely, you will need a system in place to effectively "study".
I would recommend finding a study partner or small group with which to study. This works best with people of similar academic ability. This way you can also call each other daily to check homework, especially in math.
Cornell notes are one tool that I would endorse. Classes called Avid use them extensively. Google will give you examples and directions on getting your notebook paper ready for taking Cornell notes.
For younger students, there are several acronyms that help with reading comprehension. My favorite is PLORE, which I believe was developed by teachers in Cedar Hill ISD. P is for prediction. Underline the title and make a reasonable prediction. It does not have to come true in the text. You are not allowed to copy the title in your prediction. You must write a complete sentence. Making a prediction is a little warm-up for your brain. L is for locate. Locate all the words in bold or italicized print. They are made that way for a reason. O is for organize. Number your paragraphs so the are easy to find later. R is for read and re-read. Did you know some teachers make their students read the passage a minimum of three times before looking at the questions? E is for eliminate and evaluate. This means choosing your answer. If any answers are silly or definitely wrong, put a small x to the side. After you have narrowed your choices, look back in the passage. You must prove it, with the paragraph number in which you found the answer. If it is not directly stated in the passage, put an "I" for inference. Select the correct answers, and make a good grade!