What are different startegies for black box testing?

Writing and executing test cases is an expensive task. Whatever test case is written, it should hint towards a different mode of failure. Testing strategies for black box testing are:
- Customer Requirements tests
Requirements are very important for black box testing. Each and every customer requirement should be tested. To do this, every requirement is traced to its test case and every test case to its customer requirement. The first test case is to write a most used success path ( a path that is error condition free) and proceed by planning more success paths. Some failure paths (a path that has errors in it) are also planned. Execution of tests is done so that risky requirements are tested first. It would give more time to fix the errors before the product delivery.

- Equivalence Partitioning
It is a strategy that reduces the number of test cases that are needed to be developed. The input domain is divided into classes. Test cases should be designed so that the inputs lie within these equivalence classes. For each equivalence class, set of data should be treated same by the module under test and should produce same result.

- Boundary Value Analysis
Mistakes generally occur at boundaries of the equivalence classes. Boundary value analysis guides you to create test cases at the boundaries of equivalence classes. Boundary value is defined as a value that relates to a minimum or maximum input.

- Decision Table Testing
To record business rules, decision tables are used. In decision tables, conditions represents input conditions, actions represent events that should trigger. Each column in table is a unique combination of input condition resulting in initiating an action associated with rule. Each rule or column becomes a test case.

- Failure Test Cases
The program or the application should be robust which means that it should respond properly in case or erroneous user input.