commandozx
Nothing you really need to do. be humble, show your passion to be a pilot, that abt it. No need to mug, i never mug, except just know some basics like how a jet engine works, how many engines does a 744/777/A340 has, what you wish to fly if you are selected (if you answer B737, or B767, then that's it)
Or maybe they'll ask you the range of A345.
As for the Sit test and Apt, no worries, you don't need the dexterity of a fighter pilot, I gather that you are a commando, so I think shouldn't be something you can't handle. (I'm a commando myself)
Sometimes they'll ask stupid question like why didn't you go OCS during NS, do you think Commandos are assets to SAF. (Its true cos I got this question that time)
When you make it to round two, basically its about 80% chance already, so just relax