When we prioritize our test cases, here is what we look for:

^Which functionality is most visible to the user? ^Which functionality has the largest safety impact? ^Which aspects of the app are most important to the customer? ^Which aspects of the app can be tested early in the development cycle? ^Which parts of the code are most complex and thus most subject to errors? ^Which parts of the application were developed in rush or panic mode? ^Which parts of the requirements and design are unclear or poorly thought out? ^What do the developers think are the highest-risk aspects of the application?