ところで details
Examples
by the way — moves the conversation to a new, unrelated topic
ところで、あの映画もう見た？
tokorode, ano eiga mou mita?
By the way, have you seen that movie yet? casual
ところで、来月の会議の件ですが、日程は決まりましたか。
tokorode, raigetsu no kaigi no ken desu ga, nittei wa kimarimashita ka.
By the way, regarding next month's meeting, has the schedule been decided? neutral
ところで、本日はもう一つご相談したいことがございます。
tokorode, honjitsu wa mou hitotsu go soudan shitai koto ga gozaimasu.
Incidentally, there is one more matter I would like to discuss with you today. formal
Formation
ところで、plain clauseattaches to plain clause
Notes
走ったところで間に合わない) — which needs a verb directly before
it. This entry is the sentence-initial discourse marker alone.
Related patterns
Similar
ところで shifts topic with no implied surprise, cleanly closing the previous line of talk before opening a new one; ところが shifts topic BECAUSE what follows contradicts or surprises against the expectation the previous sentence set up — using ところが for a neutral topic change overclaims a reversal that isn't there.
Lookalikes
ところだ is a PREDICATE that always follows a verb and marks where an event stands relative to now (食[た]べているところだ "in the middle of eating"); this ところで never follows a verb at all — it opens a brand-new sentence to change the subject. The two only look related in writing when a verb sits right before ところで (the excluded たところで sense), tempting a reader to parse it as ところだ with で swapped in for だ.