*** Thanks to my father and my siblings who keep enlightening me on subjects like these ***
I read a blog post and that had prompted me to write on this topic.
My mother passed away almost 2 years ago. The religious rites performed for the 13 days post her death brought in lots of discussions on the journey of a soul as per our religion. There was a quick lecture on Garudapuranam highlights as well on the 13th day. This is what I gathered -
When a soul leaves a human body(death in other words) it goes to the kingdom of Yama(the God of Dharma) to get a verification done (remember we heard stories of people reviving after being dead). Once the verification is done, it gets back to the place where it was living and sobs as its dear-ones mourn over the death of the so-and-so person and it also feels bad to shed its body and to leave them. (elders say that this is the reason the cremation has to be done ASAP). The religious rites are performed from the second day through the twelfth day and the 13th day being SUBHAM i.e. to count only the good things and move on with normal life.
Different people follow different cultural adaptations with respect to performing these last rites. I am only giving what was being observed in my community. On the 13th day, the soul leaves to Pithru loka (the world of ancestors) and it goes through various stages depending on its good/bad traits; Hindus call this as punyam/pavam. The family left behind observes monthly shrardha (shradhdha means sincerity, shrardha is the offering of pinda (a special meal) to the departed soul offered with utmost sincerity) apart from performing the same on the 27th day and 45th day (called oona-masika - I dont know the meaning though) The shrardha pinda is offered to Crows which are believed to be the form of pithrus or ancestors. After the completion of 5th monthly shrardha and before the 6th monthly shrardha a cow with a calf is offered to somebody(generally to temples) and this is called Gho (cow) Dhana (offering). My father explained to me that the soul on its journey in the pithru loka has to cross a river and this crossing is hindered by many factors. The Gho Dhana process helps the soul get through this stage with ease. Then continues the remaining monthly shrardhas and Aapdheeka, the first year's shrardha (on the day of the death in terms of lunar calendar) is performed. Only after this the soul goes through the swargha/naraka (paradise/hell) phase and is either ready for rebirth or salvation or mukthi (easy to write here :-) ) For a soul to attain salvation it has to have a nil balance of both papa/punya (bad/good). As long as there is a balance on one of these, rebirth is certain to undergo the repercussions of the good/bad. The family performs annual shrardha as a routine.
Why does the family have to keep performing the shrardha and offer the pinda (to three previous generations) every year? And how does its effect reach the soul? My gut feeling is that performing the shrardha is a form of thanksgiving. The answer to the second question is through the pithru devathas who act as agents. Sometimes we feel very happy for no particular cause - it may be because of the shrardha performed for our soul by someone (in the lineage of a previous birth). Also, offering the pinda is only for the previous three generations; if A is performing shrardha for his dad, he also offers the pinda to A's grandfather and great grandfather (if both are dead). When A dies, A's son will perform the shrardha and the offering will be made to A, A's father and A's grandfather. May be by this time, A's great grandfather would have taken another birth or attained salvation.
Some people believe that the soul retains its memory when it is in the mother's womb but the memory is flushed out when it is born. While on the earth, the soul does not retain the memories of its kith and kin from one birth to another. What a gift? Else Karunanidhi will have to have the entire assembly seats for his bloodline and there will be perunidhi, sirunidhi and all sorts of nidhi's ruling the kollywood of course with English names for their production companies.
The belief per Hinduism is that when a soul is relieved of the body before the stipulated time(age) it wanders without the body until the remaining time is elapsed. For some reason I do not believe in the existence of ghosts. I too do not know why some people were able to recollect the memories from previous births (as reported by newspapers) - this may be because God wants us to develop a belief in all these!!!