Eat some food to give you energy to study but avoid consuming excess sugar which will make you hyper and will make it more difficult to study.
An apple does a better job at keeping you focused and awake than caffeine.
Find a well lit place with no distractions around to study but don't get too comfortable or you may fall asleep.
Keep a positive attitude, it is easier to study when you are relaxed than when you are stressed out.
Since your time is limited, you have to choose what you study. Don't attempt to learn everything, focus on things that will get you the most points on the exam.
Focus on the main ideas and learn key formulas. Skip the details for now and only come back to them if you see that you have time after you have learned the key points.
Write down the key ideas/formulas on a sheet of paper and keep on studying from that sheet, repetition is important.
Highlight the important points in your notes, and text and focus on that.
Read the chapter summaries (they usually do a good job at summarizing the important points). If there're no chapter summaries then skim through the text and write down key ideas.
Study from past tests, review questions, homework & review sheets.
Take at least one five minute break an hour so that you can gather your thoughts and let your brain relax.
If time permits, try to get at least 3 hours of sleep (one sleep cycle) before the exam so that you don't fall asleep when taking your exam. Don't forget to set your alarm!