it really depends on how the fireworks are being fired that evening...
if the fireworks are being fired into "different spaces" meaning no overlap then long exposures are nice... in that case... 15-30sec at F16 would be very nice...
at the finale, usually there would be multiple bursts into the same space... in which case you may need to shorten your exposure time to say 3-5 seconds at maybe F11? (i do this coz I do not like overlapping bursts of fireworks)
So there are some "ideal" settings... but it really depends on how the fireworks are being fired to actually decide roughly what Aperture and shutter speeds to use...
Having said that... if you are shooting from Sheares Bridge, a good point would be to set your aperture and shutter to expose the backgrd properly, then use that setting to shoot your fireworks... should give a rather nice picture...
Do a search on Singapore Fireworks Festival in events subforums... that should give you a lot of info already on what to expect and what cond the pple on the BSB used...
Do take note that due to movement of heavy vehicles on the bridge, pictures would often be a little blur due to shaking...
hope i haven't confused you... sorry for the long blabber... just my $0.02