Communicating with the Dead

Without question, our prize possessions are the children we raise, and it is they who remain our legacy after we depart from the world.
Traditionally, children pledge funds to tzedakah and perform other good deeds in the merit of their deceased parents and loved ones.
What are the legal and philosophical arguments in defense of the idea that the deceased may enjoy the merits accrued by the good deeds of others? What if the individual was less-than righteous? Can the tzedakah by community members benefit their soul as well? What makes Yom Kippur a most propitious day to pledge tzedakah for the deceased?

“Either way, they are My children” [Talmud].
Blood is thicker than water, they say. The bonds of family are the anchor of an emotionally and spiritually healthy life. But what happens to these relationships after one passes on? Do we “meet again on the other side”? Do families stick together in the hereafter? What about teachers and their pupils? Is this contingent on whether the two are buried in close proximity?
Do the souls of the departed maintain a relationship with those left behind? Do they relate to and empathize with the trivialities of our corporeal existence? Does prayer at their grave-site invoke merit on their behalf?

Emulating G-d’s example, we are encouraged to visit and tend to the sick. Our presence is assured by the Talmud as having the power to heal a portion of the patient’s suffering. Does Halacha provide guidelines for the visitor in the performance of this mitzva?

Prayer, too, is an integral part of this mitzvah. What particular prayers should be said for their recovery? What about assisting the individual in the recitation of prayers during their final moments?