[Dovecot] Which comes first after postfix, dovecot or cyrus-sasl?

[Mike]

Hello Group,

I have a fully operational postfix server (ver. 2.1.5) set up to host
separate domains with virtual accounts.  Tests show that the postfix
server is successfully sending email messages by way of telnet and it
receives and stores new email messages to virtual accounts from the
internet.

Now I want to move forward and integrate dovecot imap server to work
with postfix.  I understand that I need some way for users to be
authenticated by the imap server, so I also want to use cyrus-sasl. 
Ultimately I want to provide a webmail interface using apache and
squirrelmail to my users.

I'm finding many different examples on the net that install the
software components in very different steps.  I'd like a push in the
right direction as to what is most logically installed next to achieve
the goal.

Thank you for your help in this regard.

Mike