Acting as a 接続詞（せつぞくし） (conjunction), さて
is a word used when one wants to change the topic of conversation, or is ready to move on to a new point. Usually it is translated as ‘well’, or ‘well then’.
will appear at the beginning of a sentence, before the speaker highlights what the new topic is.
Well, let's head off soon.
Well, first things first, let's have a toast.
is extremely rarely written in kanji, 扨（さて）
may be seen every now and then. Both of these kanji have the same meaning of ‘now’ (now being the beginning of something new).
Now, is there anyone here that knows the answer to this question.
Now, please place that luggage on top of this box.