The requirements are not exhaustive but couple of things to
note:
Firstly, you need to do well in your MINDEF psych tests prior to
enlistment, and dare to jump parachute, dare to climb mountain,
dare to do everything (show good attitude and willingness to
try).
Secondly during your BMT, you should possess a good attitude and do
everything to your best even if you may not be the best. You should
possess a helpful personality and help others out, as well as show
your potential to lead others by a handful of tasks that you may be
asked to take the lead.
Your fitness should be unquestionably good, though it is not a
requirement to get IPPT Gold to go OCS (but must pass definitely).
I have had a platoon mate who barely passed IPPT in BMT but made it
to OCS (no idea how he did it also) but during OCS before
commissioning he failed to pass the IPPT, so in the end went Out Of
Course (OOC).
Thirdly, you should interact well with your peers and gain their
friendship and respect. There will be a grading exercise where your
peers evaluate you and vice versa. If you gain high peer support,
it will help your case to make it to OCS. Anyone that others hate
to the core is unlikely to make it to OCS as he can't even motivate
his peers or gain their respect.
During the BMT outfield exercises (viz chiong sua), you should be
spontaneous and volunteer to lead the section / platoon during the
simple missions. Don't sleep on the job though Zzz Monster is
always prowling, and be on the ball and help others out. Just work
on ensuring that you don't cock up the mission when you volunteer
to lead the section.
Good luck to you 
