Study 45 minutes then give yourself a 15 minute break.
For an all nighter I revised 45 minutes, then lay on my bed for 10 minutes then check the net for 5 minutes then carry on.
I managed to do around 6 hours.
Read the textbook, make notes.
Read notes, highlight key points that weren't in the text book.
Write up all the notes on paper with diagrams etc.
Highlight key points by going through what you've written
Put it in a file.
1 Week before the exam (or how ever long you think you need) revise 45 min, break 15 min.
Also I found that by darkening the entire room, and using a table lamp (£15 Sainsbury's) it helps with distractions, and keeps you focused on the task at hand. Then when you need to relax you can lie on your bed and close your eyes for a bit.
Well that's what I did anyway.