visit this website
http://www.kppsc.gov.pk/interviewtips/index.php
you should also have knowledge on the following:-
1. islam ( bsics ( tuahid , risalat , akhirat ) , ayatul kursi , 06 kalmey , darood sharif , janaza etc.
2. pak affairs ( geoghaphy , important office holders , constitutions , imporatant dates , knowledge of sindh provice )
3. job profile ( whats poice? , ASI ? , relevant laws? police structure etc)
4. general knowledge/current affairs ( ready newspaper daily and watch talk shows )