1) Do I always need to press the button on the shift lever when shifting?
If it has a button / lever, then yes
2) When stopping for a minute or two at a traffic signal, should I keep it in D mode or change to N?
Put it in P or N- For quick stops, keep your foot on the brake. P>R>N>D
3) Which position should I select when going uphill or downhill?
[I]Uphill- Just keep driving in D, if the climb is too steep, then 3 or 2. That will lock the gears, so it won't keep on upshifting / downshifting.
Same applies to driving downhill.
i.e descending Kallar Kahar- Keep it in 2. Make sure that your speed is very low before shifting to 3,2 & 1 from D.[/I]