There are various techniques you coud use... you have to find the right one for you. I'll give a few tips, and I'm sure others will add their own! :-)
- Don't revise for too long at a time, and take sensible breaks.
- Create a timetable of study time, but don't necessarily lock yourself down to each subject.
- Try anacronyms... RSPCA is one, or DR ABC (for danger, responce, airway, breathing and circulation), or the way we all learned the colours of the rainbow... Richard of York....
- With vocab for French/Spanish/German etc, use look/cover/write/check. And just try to practice using the language when you can.
- Try to use a variety of sources. Use the bbc - they have many good ideas for revision tips too. For example, if you're really bored of revising Romeo and Juliet, ask your parents to let you watch the DVD of it. Don't think this is an alternative to proper study, but it will be an additional aide memoire.
- Use colour - highlight things, or use different coloured pens. This helps to keep your mind interested!