Links

PET:
http://www.cambridgeenglish.org/exams/preliminary-for-schools/how-to-prepare/

First:
http://www.cambridgeenglish.org/exams-and-qualifications/first-for-schools/exam-update-for-2015/

KET:
http://www.cambridgeenglish.org/exams/first-for-schools/how-to-prepare/