it's not really necessary na ilagay sa neutral. pag light traffic, lagay mo sa "D". pag heavy traffic at nakahinto ka palagi, might as well shift to "P" so you don't have to step on the brakes.

"S" i think is for "second", usually used in adverse road conditions or uphill. it could also be S" and "M" (or - and +)...gamit nila sa manumatic cars.