Depending on what ones you are doing, I would advise to check out any LC Science books you find. So if you're doing the Biology ones then look at LC Biology book in your school. This is what I did when I did mine in 3rd year.
The biology one is off the OLD LC biology syllabus. Find an old biology textbook (Siobhan Scott: Senior Biology)
The physics one is just Ohms Law.
The chemistry one is just repeated measuring of pH after each dilution. You just need an accurate pH meter.