Performance tuning in Pgsql

Dear all,

I am researched a lot about Performance tuning in Pgsql.

I found that we have to change shared_buffer parameter and
effective_cache_size parameter.
I changed shared_buffer to 2 GB but I can't able to locate
effective_cache_size parameter in postgresql.conf file.

Also i want to change my WAL directory to seperate directory. Same I
couldn,t locate pg_xlog or how to change it.

I am very new to postgresql. Please help and guide me if any other thing
needed for Make our Postgresql Server Faster and give better performance.


Thanks & Regards

Adarsh Sharma