What are the benefits of transferring karmic fruitfulness and how is this done by Buddhists?
Make merit is the core of the buddhist practice and is done by being resolute and practice deeds (through mind, speach and body) of generosity, renunciation and goodwill. This will gradually lead to the decrease of the defilements (greed, ill-will and delusion) and to the maturation of the eight factors of the Noble Eightfold Path.
Sharing of merit is one of the Ten ways of Making Merit because is a expression of goodwill and generosity and is done by inviting others to rejoice in the merits that you have done (which by itself is also a source of merit) or be intended that they do so. In other words, the more you practice merits, the closer you are to Nibbana. If you hold the intetion that others also make merit by rejoicing with your merits, this means that you are resolved in goodwill and generosity (which is right view/right resolve), thus, this is again a souce of merit.
May all beings — without limit, without end — have a share in the merit just now made, and in whatever other merit I have made.
Those who are dear & kind to me — beginning with my mother & father — whom I have seen or never seen; and others, neutral or hostile;
If they know of my dedication of merit, may they themselves rejoice, And if they do not know, may the devas inform them.
By reason of their rejoicing in my gift of merit, may all beings always live happily, free from animosity.
May they attain the Serene State, and their radiant hopes be fulfilled.
If someone understands the value of giving, does it out of the kindness, without wishing for anything in return, it is a truly meritorious deed (kusala kamma). This is the highest merit. Thus understanding Dhamma (true nature of the world) leads to spontaneous meritorious actions done with a joyful heart; this leads to saddha (true faith) , citta pasada (joy), and adhimokkha (resolve) to get the maximum impact of it.
“This world” of 31 realms is very complex. Nothing happens due to a single cause and nothing happens just by itself: Multiple causes lead to multiple effects. People are born with different levels of not only wealth, but also different levels of health, physical appearance, capabilities, etc. These are the results of kamma (good and bad) accrued over very long periods in the past.
Due to our past acts, both good and bad, we get into “sansaric relationships” with other beings; this is how we have friends, family, and enemies. These things do not happen by chance. Everything happens due to a cause, a reason; but since results (vipaka) can materialize later, even in future lives, we cannot see this “cause and effect” in most cases. When we do something harmful to another being we become indebted to that being; that debt will have to be paid with interest that is many many times over. When we have such debts, the nature has set up many ways to pay off such debts. The correct way to pay back old debts is when one does a good deed, is by transfering merits of that good deed to old creditors called “pattidana”.
All intentions have kammic energy. You may remember that the Buddha said, “Cetana ham bhikkave kamman vadami”, or “Bhikkhus, I say intention is kamma”. And kamma is the fundamental potential energy for everything in this world. When one is “transferring merits” by sincerely saying that “May so and so receive merits from this good deed that I have done, one is broadcasting one’s intention. It is possible to “give Dhamma” or to “give kusala” too. In fact the Buddha said, “sabba danan Dhamma danan jinati” or, “from all kinds of giving, Dhamma giving is the most meritorious”.