Tonight - Sunday night - one may not do any work, nor eat anything, until one has checked the house for Chametz.
Before one starts searching the house for Chametz the entire house needs to be cleaned, and the Chametz that one plans to use until mid-morning on Monday morning needs to be put in a secure place.
First one says the Bracha:
After the search is complete one says “Kol Chamira” declaring that "all Chametz one isn't aware of" to be “ owner-less and worthless like dust”.
This declaration constitutes a Halachic “destroying Chametz”, which is why one shouldn't interrupt between the Bracha, the searching and the Kol Chamira with anything unrelated to the search.
One may appoint other members of the household to help with the search, as long as they are over Bar/Bat Mitzva.
The search is done using a single candle which provides the optimal light for searching. A torch (like a Havdala candle) is not allowed – as it’s a fire hazard and it gives a flickering light – and if it was used one needs to redo the search.
Search under all furniture, inside all closets, pockets of all clothes worn in the past year, schoolbags, purses, cars and anywhere else where Chametz could have been placed accidentally or purposely by adults, children or toddlers.
Source: Kitzur Shulchan Aruch 111:1-10
There is no need to turn off the electric lights while searching with a candle, since with more light it’s easier to find Chametz.
After searching with a candle in those places where it’s safe and convenient to do so, one should continue with a flashlight, so that one can search safely and calmly without fear of burning down the house.
Source: Rabbi Shimon Eider zt”l, Halachos of Pessach, Vol. 1, page 86
One does not say מִזְמוֹר לְתוֹדָה nor לַמְנַצֵּחַ from Erev Pessach until Isru Chag.
Sunday, 13 Nissan 5773