を
indicates direct objects
で
indicates where event describe by the verb takes place
へ
indicates goal of movement. may replace に only in goal of movement sense
に
goal toward which things move, and the time at which an event takes place
when do you need に
OK
-days of the week
-numerical time expressions (10:45, september)
NOT OK
-relative time expressions (today, tomorrow)
-time interval expressions (every day, every night, when)
UNNECESSARY BUT OK
-describing parts of the day (in the morning/night, weekend)
put these in order: topic verb object time place
topic time place object verb
put these in order: topic frequency verb goal time
topic frequency time goal verb
が
used with います、あります、きらい、すき