Do any and all the practise exams you can get.
I used Aviation Theory Centre textbooks (and the sample exams in the back of that) as well as Dyson Holland practise exams, passed first go.
DH give you (i think) three exams in the book, along with worked solutions, so its a great way to find out what they are asking you.
I havent used them myself but have heard nothing but strong recommendations for Bob Tait's stuff too - does anyone know whether his practise exam CDs have vastly different questions to the ones in his textbooks, or do they double up??