First, what runlevel have you ?
If you have runleve 3 (as example) go to /etc/rc.d/rc3.d and check the symbolic links that starts with S .
In example, you have the service sendmail and squid, you want squid loaded first than senmail, at /etc/rc.d/rc3.d/ you will find
S19 is loaded first than S30, you need to assign to S30squid a less value, or give to sendmail a value higher than squid.
Good luck !
You can use