We use Clash Caller to help plan our war attacks. Primarily this ensures you can select a base, then plan your attack and train your troops for it safe in the knowledge that no-one else will hit it in the meantime. In addition we use the notes section to provide some tips on how to exploit weaknesses in a given base (notes can also be used to seek feedback on your plan), and we now label certain bases with a target to help our general war strategy.
At some point during Preparation Day, some of the enemy bases will be labelled with targets. The system is as follows: