The Yizkor prayer is recited 4 times a year: on the closing holiday of Passover, Sukkot, Shavuot and on Yom-Kippur. Recitation of the Yizkor prayer takes place after the Torah reading during the morning prayer. It is customary for those with two living parents to exit the prayer hall.
The very text of the Yizkor memorial prayer includes a pledge to donate money to charity, without giving a vow. However, if this sum is not donated, there is no assistance to elevation of the soul.
Donating during the holiday is forbidden, therefore the donations are made either before the holiday, or after it.
It is very good to recite Yizkor for those deceased, who to your knowldege have no one to recite Yizkor for them. If in these circumstances a person cannot recite Yizkor himself for whatever reason, he can pay another Jew to recite the prayer in his stead. Doing this would count as if this person recited Yizkor by himself in memory of a deceased person.
Order a Yizkor recitation
In order to recite Yizkor we need to know the name of the departed