What does it mean to "be prepared" for class?
Read the syllabus or other instructions, complete any assignments or readings on time, and bring any necessary materials to class with you, if applicable.
Have your friend take notes for you while you are on vacation.
Get 8-10 hours of sleep, eat a complete breakfast, exercise for 30 minutes or more, and take regular breaks from studying.
Stop to get coffee and a bagel for yourself before you attend class, even if it means you will be a few minutes late. Nobody will mind if you sneak in a little later.