The Prophet would perform i tikaf for ten days every Ramadan. In the year that he died, he performed it for twenty days. This is related by alBukhari, Abu Dawud, and ibn-Majah. The Prophet s companions and wives performed i tikaf with him and continued to do so after his death.
Saum i.e. the fast begins with Suhur – the pre-dawn meal and ends with Iftaar – the food taken at the dusk. Taking Suhur is Sunnah and though it is not mandatory, Prophet Mohammad (peace and blessings be upon him) had advised the Ummah to take the pre-dawn meal i.e. Suhur to begin the fast.
Because this is not specifically stated which of these nights is the Lailat-ul-Qadr, for catching this night, some people do the Itekaf that means they confine themselves to the mosque during these ten days, stay up and pray during the whole of these nights.