A few minutes preparing for class should make it much easier to get more out of class.
You are less likely to forget to turn in homework.
You will impress your professor.
It is a good skill to have for meetings in your professional life. Going "cold" to a meeting is not good.
Often you may be confused about something the first time it is covered. Getting to that stage before class means you can spend class time actually understanding (since you know what you are confused about). You are ready to ask questions, pay attention, etc.
Guidelines on how to do it
Simplest step: Check the schedule to know the topic for the day and also to confirm what is due. Do this as you wait for class to start. Add it as the title for that day's lecture notes.
Next level: Within 24 hours of the class starting, ask yourself what you know about the topic. If it is totally unfamiliar to you, spend about 10 minutes reading about it in the textbook or on the Internet.
Read the material in the textbook before class, identifying the things you understand and the things you don't.
Requirements for credit
Describe what you typically did to get ready for class before working on this Gem.
For each of the guidelines, identify two things about it that would work well for you. These can be specific to certain classes or in general.
For each of the guidelines, identify at least one thing about it that might be a challenge for you. It can be specific to a certain class or in general.