Considering whether a particular course of action is right or wrong is ethical thinking.

Ethical principles provide a starting point when thinking something through and they play different roles in different ethical frameworks. You might use more than one ethical principle to shed light on an ethical question - in just the same way that you might use different colours of light to view a scene. 

Ethical principles are not used mechanically. In a particular situation, some ethical principle (or principles) will be more appropriate. And in each situation you need to judge which principle(s) carry most weight. This will help you with concerns such as how to manage conflicting interests.

Doing good - avoiding harm