For most services:
Edit /opt/iic/conf/config.xml and change debug level from error to debug.
For jabberd:
Edit /opt/iic/jabberd/jabber.xml and search for elogger. Under this element, find the debug attribute and set to 1.
Restart services by using /opt/iic/conf/control-services.sh stop and /opt/iic/conf/control-services.sh start.
Logs are in /var/log/iic, except for the client connector (jadc2s) which uses syslog.
You can also enable logging from the console, but that setting only lasts until the server is restarted and must be enabled service-by-service.
Logs are rotated according to the size and number specified in config.xml. In some cases these numbers must be made larger to capture enough tracing.
Apache logs are in /usr/local/apache2/logs.