Oracle Enterprise Manager / Cloud Control

Environment Overview
To show info about currently running OMS including URLS, ports, and paths:

cd $OMS_HOME/bin
./emctl status oms -details

Reset Weblogic Admin Password
12c , 13c Cloud Control: Steps for Modifying the Password for Weblogic and Nodemanager User Accounts in the Enterprise Manager Installation (Doc ID 1450798.1)
Reset Weblogic Admin Server Password
Querying the Management Repository

• 11g Management Repository Views
• Digging deep in Oracle Grid Repository for Information - Sagar Patil
• Querying the Oracle SYSMAN MGMT$ Views SYSMAN.MGMT$
• Some more useful undocumented OEM 12c repository tables/views

EMCLI Command Line Automation

• Using EM CLI
• EMCLI Verb Reference
• Advanced EM CLI Script Examples
• Using EMCLI to Create Preferred Credentials
• Set Credentials For Many Database Targets Using EMCLI ( Doc ID 744409.1 )
• Jump into the EMCLI Presentation
• EMCLI Python script to create users

Agent Troubleshooting
Interactive config refresh failing
I found the interacive screens to refresh a host config did not always work. This includes using the "Refresh Configuration" button on the host screen or the Enterprise-Configuration-Refresh_Host_Configuration to kick off a configuration refresh job. From the affected agent home run:

./emctl control agent runcollection hostname.com:host ll_host_config 

If all is good you will get a "EMD runCollection completed successfully" message returned.
Discovering new Oracle Homes
Discover and promote Oracle Homes as Targets