1.Download latest Percona tool kit.
Download from here ,
http://www.percona.com/downloads/percona-toolkit/LATEST/
2.Percona tool kit Installation steps here,
http://knowmysql.blogspot.in/2013/09/percona-tool-kit-installation.html
3.After installation enable Slow query log variable in MySQL
a.Enable through my.cnf for permanent
add below two lines,
slow_query_log=ON
long_query_time=5
Restart mysql
b.Enable for the current session
login to mysql server
>set global slow_query_log=ON;
> set global long_query_time=5;
4.By default slow query log file will be in MySQL data directory
go to mysql data directory and see hostname-slow.log
wait for few hours to get the slow queries in the log file.
5.Now run the pt-query-digit to see the slow queries
#pt-query-digest /mysqldatadirectorypath/hostname-slow.log > /backup/slowqueries.txt
6.Now evaluate the slow queries.
#less /backup/slowqueries.txt
here first in overall session you can see the total details
Second you can see the list of top queries in rankwise.
Third full details of each queries.
in the each queries the main things to see is,
Total number of execute time of the query from by 95% column.
