[GENERAL] good settings for DB parameters such as shared_buffers, checkpoint_segment in Postrgesql 9

[AI Rumman]

I am going to install Postgresql 9.0 for my running applicaiton which is at
8.1.
My Db size is 3 GB.
Server Specification:
  dual-core 4 cpu
  RAM: 32 GB
  OS: Centos
What will be good settings for DB parameters such as shared_buffers,
checkpoint_segment and etc.
Any help please.