There are two types of sareis.
The first one is done like the Baito style, which will be announced by clappers and bells.
At the beginning sit in SEIZA and don't put your cup out yet.
After the two clappers followed by one bell of the Jisharyo,
Put out your cup.
When the tea is being served, put out your cup alone, if you are the first person in a row, otherwise put your cup next to your neighbours.
After your neighbour has been served as well, do gassho and drink the tea.
Then place the cup back in front of you.
When the Jisharyo walks by the second time, bow and put your cup back behind the cushion.
After the one taku, 2 bells and again 2 Taku by the Jikijitsu, sit in Zazen.
The other style of sarei is at night.
When sarei is announced, sit in seiza and place your cup in front of you right away.
Then after receiving the candy and tea, do gassho and drink the tea.
After the Jisharyo has passed a second time, bow and put your cup back behind you and right away change into the zazen position.