Accurate: Can it explain lots of data and real-world observations? Relatively simple, broad, 3 or 4 factors
Consistent: Are there very few exceptions and does it fit with other theories?
Scope: Can it explain things beyond the current data or research findings?
Simplicity: Is it less complex than other theories that explain the pattern of data similarly well?
Fruitfulness: Does it generate new, testable hypotheses?
Falsifiable: Can it be tested and proven wrong?