InnoDB Default Storage Engine

[Angelina Paul]

I want to change the mysql default storage engine from MyISAM to InnoDB.
What are the  steps involved .Is it edit my.cnf file and add a line
default-storage-engine=innodb and restart the mysql server? How I can bring
my databases with mixed storage engine down without any data loss. What
steps I have to take if I encounter a page corruption in innodb tables. why
I am getting a message "*Error*: *No query specified*"  when I run a show
engines\g commands -version (5.0.45)

Thanks,
Arsh Paul