Here's what I did to pass all the exams during the year through self study.
Read through the Trevor Thom books, answering the questions for each chapter after I'd read it. If I didn't get a high score or didn't understand why I'd got it wrong, then re-read that bit.
After reading a book, used the Oxford PPL Exam Prep CD (which came as part of my PPL study pack), repeating these until I got a pass every time.
Also used the iPhone App from Great Circle for one or two modules to practice when I had a few minutes to spare on a commute or other odd times. The spelling is atrocious, but there are detailed explanations behind the answers if you get them wrong.
I aimed to do about one exam a month - some are much easier than others, but which ones will depend on your own experience and interests.
Suggest you do the Air Law first because most flying schools insist you have this before going solo (although it isn't a legal requirement). Be aware that it's arguably the most boring module
so all downhill after that.
I'd also recommend the Oxford VHF audio CD, although it doesn't include the latest changes to phraseology (such as Basic Service, Traffic Service) for when you come to do your practical VHF radio exam.