How can we deal with selfish people annoying one ?

I think the best way to deal with selfish people is by first trying to understand where they are coming from, i.e what causes them to be selfish. You may discover that they are selfish because they felt that their generosity in the past was abused. It may be an eye-opener to discover the cause of people's selfishness.

From there a person can be advised out of their selfishness or in some cases shown how their selfishness affects the people around them.