mysql replication for certain dababases I am new to mysql and I have a query in regards to mysql replication. 

Currently, I have a master database that replicates to four slave servers at the moment. I would need to set up a few replication servers(as slave) but these will replicate only a few databases. How would approach this issue?

Should I be using something like this on slave /etc/my.cnf? 

replicate-ignore-db=db_name

Can I set something on slave configuration stating exactly which databases and tables to be replicated? 

Should the changes happen only on the slave configuration or on master as well? The reason being this master server currently replicates whole lot of databases to other slaves which will remain as it is.
I would avoid the replicate-do-db option due to the restriction on cross-database replication and users not fully qualifying a database name or not specifying "use dbname;" (it will execute on master but not replicate to slave).

Use this option instead (put it in my.cnf): 

replicate-wild-do-table=dbname1.%

replicate-wild-do-table=dbname2.%

Or you can specify the tables, replace % with table name, one on each line.
http://dev.mysql.com/doc/refman/5.0/en/replication-options-slave.html#option_mysqld_replicate-wild-do-table

This link should help get you started:
http://dev.mysql.com/doc/refman/5.0/en/replication-solutions-partitioning.html