What you should think.

ISSB Stand For Inter Services Selection Board

Before start talking about the days of ISSB, there are some tips which you guys should know are, "you should think that you are not less then any one, the candidates those pass there initial are all equal, there is one thing in which any one will be weak, no one is perfect. Be confidence and trust on Allah.
After the Passing your initial (medical, physical, interview) don't for the call later just start your training. After getting call later you will not have enough time to ready for ISSB.
Start running and do chin ups and jump more than 4 feet. Do other PTs and offer 5 time prays. Get information about the Army which you are going to join.