I’ll tell you the method I used. First read the first and the last paragraph of the scenario, so you develop an understanding what the scenario is all about. Then go on to read the question requirements. In the question look for key words like internal, external, business process etc. These key words will give you an idea of what model you may be needed to apply. Then read the whole scenario and answer the questions.
Apart from this I can’t think of any hint to solve the scenarios except for practice!