No lah usually interview they just ask whether you want or
not,then there a medical check up,etc.
If you don't want,when the officer ask u whether u like about the
unit,just say you don't like,etc,are you outgoing?NO
hahaa,basically just perform badly can liao and durning medical
check up,if you have some illness,just declare,they will then not
accept you 
Last time i kena NDU interview,that before enlistment,they ask me
whether i like sports etc,i put no,they ask abt my character i say
i am a quiet and shy boi LOL,and durning medical check up i say i
got nose allegic,last time got asthma and OFF i am to TEKONG
hahahaaaaa so don't worry lah
and bear in mind i never downgrade leh still Pes
B