If you just want to get Dovecot running with typical configuration in a typical environment, here's what you'll have to do:
You'll probably be using PAM authentication. Make sure /etc/pam.d/dovecot exists. Here's a working example:
auth required pam_unix.so account required pam_unix.so
If you're using something else, check passdb and userdb settings.
You can let Dovecot do its automatic mail location detection, but it that doesn't work, you set the location manually from default_mail_env setting. See MailLocation for more information.
Make sure that all software accessing the mboxes are using same locking methods in same order. The order is important to prevent deadlocking. From Dovecot's side you can change these from mbox_read_locks and mbox_write_locks settings. See MboxLocking for more information.
If you're using /var/mail/ directory for INBOXes, you may need to set mail_extra_groups = mail so Dovecot can create dotlocks there.
Check imap_client_workarounds and pop3_client_workarounds and see if you want to enable more of them than the defaults.
If you're going to use Dovecot's POP3 server, you'll need to add pop3 to protocols line in configuration file.
You'll also have to set pop3_uidl_format setting. If you're migrating from another POP3 server, see [wiki:Migration migration page]. Otherwise set it to Dovecot's default:
pop3_uidl_format = %08Xu%08Xv
If you intend to use SSL, set ssl_cert_file and ssl_key_file settings. Otherwise set ssl_disable = yes. Easiest way to get SSL certificates built is to use Dovecot's doc/mkcert.sh script.
By default Dovecot doesn't allow users to send passwords unencrypted to the server. Usually if SSL is enabled, it's a good idea not to allow this. However, if you don't offer SSL for some reason, you'll probably want to set disable_plaintext_auth = no.
If you're using NFS or some other remote filesystem that's shared between multiple computers, you'll need to set mmap_disable = yes and change lock_method to fcntl or dotlock. These settings are only used for handling index files.
Note that storing index files in NFS doesn't work perfectly yet, but as long as mailboxes don't get heavy concurrent accesses from multiple clients, it should work well enough. In any case you might want to store the index files in local disk instead. This is done by appending :INDEX=path to default_mail_env. For example:
default_mail_env = mbox:~/mail:INBOX=/var/mail/%u:INDEX=/var/indexes/%u
Remember that if you're storing indexes locally you can keep mmap_disable = no (which gives better performance).
See RunningDovecot and [wiki:Logging Logging].