MYSQL Replication

HI,
I've a MySQL server with 250 websites db.
I wanna create a redundant server so if this server goes down the other one
can save me!
I see that I can set the replication.
I've tryed to simulate two server in my office.
But my questions are:
1) I need to create all the db with all the tables in each server in order
to make the replication works? Or it's create them automatically?
If yes.. how can I set my.ini?

thanks a lot for your help!!!
Bye