A lot of teacher will post "study guides" that tell you which parts of your textbook you need to be familiar with. Use these as a resource when you're making your study guides. Even if they don't publish a guide, they will often mention during class what's most important to know for the test: jot down what they say in your notes to review later.
Review your textbook.
If I have a study guide, I'll look at it before I start reading so I know what to pay the most attention to and take notes on. I leave my laptop open to immediately take notes on each important section. For example, if the study guide says, "Be familiar with the Pure Food and Drug Act," I pay close attention to the section of my textbook that talks about the Pure Food and Drug Act, then immediately type up a summary in my Word document to make sure I've understood what I've read. By doing it this way, I have a completed study guide by the time I've finished reading each chapter.
Review your notes.
It's a lot easier to read a condensed, typed version of my notes than the scattered, handwritten notes I usually take. Reasonably soon after a lecture, I type up the most important parts of my notes while the material is still fresh in my brain. This also helps me solidify what I've learned and prepare for quizzes.
Include important vocabulary terms.
If there are terms you either have a hard time remembering or the professor has stressed are important to know, I would also include them in your study guide. This is especially important when there are a bunch of similar terms you need to know the difference between (for example, I need to know the difference between dependence and addiction, so those terms are included in my study guide.)
Use your own words.
While copying and pasting is a lot easier, it's important to write definitions and explanations in your own words so you can really understand what they mean.
Include information you didn't understand in the past.
If you missed a quiz question on something, consistently misunderstood a concept on the homework, or really had a hard time grasping something, figure out what your misconception was and then include it in your study guide so you don't make the same mistake twice!
To make my study guides seem manageable, I try to get all the information for one chapter or unit on one page by using columns and not getting too wordy. (It also saves on printing costs.)
In case you're wondering what one of my study guides look like, here's a screenshot of one:
It's nothing pretty or complicated, just something that has the potential to really boost your school performance!
What are your favorite tricks for studying more efficiently?