Pay attention during lectures and tutorials. The temptation to
switch off or skip them is very very great. Trust me, once you pay
attention, your need to do self-revision will cut down by about 30%
to 40%. Never just blindly copy what is on the whiteboard/projector
screen. Listen to your tutor/lecturer and understand the
fundamental concept.
Of course, you can try practising. For me, the only subject that I
practise a lot on is H2 Maths. At the start of my j2 year, I
couldn't understand a single thing about Vectors and Complex
Numbers. I just piah qns on these 2 topics for 3 months and somehow
I manage to understand the questions better. Of course, doing
prelim papers from other schools helps too *thinks back about the
hours burnt in ang mo kio library doing prelim papers after prelim
papers*.
For physics, TYS is the most important. Period. Chemistry... Just
go practice answering questions on chemical trends (esp chemical
bonding). You need to write concisely and score on all the
keywords. Of course, organic chemistry is mug+application, physical
chemistry is really lotsa practice, inorganic chemistry is just
pure mug (just mug and you are likely to score full marks on any
inorg chem qns).
Most importantly, have the will to go study. Discipline is what it
takes. Well, actually, I started only in the second half of the
year which is quite late. Besides, I also had to train to get that
NAPFA silver (didnt pass a single NAPFA until my j2 year). So I
guess it is possible to juggle various committments. Just be
focused and manage your time well.