"I just start daydreaming"
Become an active learner. Always work with a pen and paper. Focus on a specific task, not a specified time for your study.
"I often fall asleep when I'm supposed to be studying"
Try to get to bed on time over the coming weeks. A tired brain is very unproductive. Get some genuine rest at the weekend. Be sure to get regular exercise, even just a walk around the block at night to clear your head.
"I keep thinking of other things while I'm studying"
Divide the study session into smaller, short-range goals which demand your full attention e.g. vocabulary or poetry test. Keep a 'reminder pad' beside you, a little notebook to jot down something that strikes you (someone to call, a job to do, etc.) and deal with it after the study period. Having made a note of it, you can more easily re-focus on your work.
"I can't focus because I'm anxious about the exams"
Try to limit yourself to your immediate concerns, the things you have some control over (preparation for the upcoming revision test) rather than the things you cannot determine (like what questions the examiners will choose for this year's English Lit paper.)
"I'm constantly interrupted by other people"
Study in the location most likely to offer peace and quiet. Ask for consideration from family members over the final run up to exams. Never have a TV, phone, computer game, or music system within arm's reach while you are trying to work. Make a rule of not taking phone calls within certain defined periods.