Nothing beats reading the material and absorbing it as you go. But, if you are preoccupied (for whatever reason) these suggestions may help you squeak by. (since you have 30 days left, maybe read a chapter every other night).

Do you have a text book? If so, skim the chapters. If there are questions at the beginning that identify what you should know by the end of the chapter, make sure you can answer those questions.

Pay special attention to names, bolded/italicized text, and information that is separated from the general text body. Also, see if there is a summary/synopsis at the end of each chapter, this can be helpful.

Is this a self study course? If so, the above will be your biggest help. If not, go through material you have completed for the course to date. This will refresh any information that you have gone over already.

See if there are old exams that you can study from or if you have a study guide, take the sample exam to see where your strengths and weaknesses lie.