Assume that there is life after death. (I acknowledge that many would
say that the assumption is wrong; but assume that for your
answer/comment.)

What do we need to do in life (this is before we die), to improve the
quality of our after-life?

?Quality? may mean ?happiness? or ?well-being? in my question; but I
am open to other meanings.

I would like to learn views from as many
religions/philosophies/science as possible, including some uncommonly
followed/accepted, as well as opinions from readers of Google?s
Answers.

Either a summary or an exposition for each of these, with sources for
further reading/research would be highly appreciated.

Is there commonality from across different views?

I have reviewed questions with   "life after death OR hereafter 
and found the following that could be a start.  Especially the second
one is full of links to appropriate websites:
http://answers.google.com/answers/threadview?id=607752
http://answers.google.com/answers/threadview?id=431764
http://answers.google.com/answers/threadview?id=117632

As to your first question, Christian faiths and Islam certainly have
the feeling that one's acts in this life have an effect on one's
reception in the hereafter.  That is the prize for upholding the moral
tenets of a religion.  I believe that the previous pope reinterpreted
the concept of pergatory, doing away with the hellfire.
Non-religious philosophies use different arguments to justify why it
is good to be a good and just person.

Religions that believe in transmigration of the soul (Buddhism,
Jainism, ?) - that one will be reincarnated (made flesh again) -  also
believe that one's character in this life will influence the form in
which one is reincarnated, i.e., maybe as an insect or a "filthy" (in
that religion) animal if you did not behave worthily enough to return
as a human.

The archaeological findings in graves indicate that religions in many
parts of the world believed that the deceased person needed to be
supplied with everything he or she could need in their next life. 
This suggests that the people not only believed in a life hereafter,
but also that to make it comfortable, a person would need to have
along what was appropriate for his or her position in this world. 
I.e., you CAN take it with you  - you BETTER take it with you -  if
you want to be as well off and respected in the hereafter.

Well, that is a start, and may elicit some corrections, but they will
enliven the discussion.

The person above used mumbo jumbo, here's the easy answere

Christians - love god, hate gays
Jews - Love god, love seinfeld
Muslims - love god, pray a shitload
Hindus - Love god, all of them
Buddhists - love yourself, keep it real
Atheists - love nothing, hate the people above
Scientists - love robots, hate monkeys

The common part of it is love god unless your the bottom three. Also
they all hate each other. The only cool person is the dolly llama who
says just be happy and nice.

Popov

Speaking of mumbo jumbo, what is a "dolly llama"?

Little Inca girls play with them..  The better off ones play with dolly vicunas.

I am not exactly a very religious person,but from wht i know,Hinduism
has 4 yugs or ages.The satyayug,tret?yug,dv?p?ryug and kaliyug.These
yugs or ages have different significances.These yugs start when men
sope only the truth and led a virtuous life and now in the Kaliyug is
when men are selfish and liars.In this yug even uttering Gods name
gets you to heaven.