This may be an attempt to test a theory with a typical case or it can be a specific topic that is of interest.
Research should be thorough and note taking should be meticulous and systematic.
It is best if you make yourself a short list of 4 or 5 bullet points that you are going to try and address during the study.
If you make sure that all research refers back to these then you will not be far wrong.
On the other hand, it is argued that a case study provides more realistic responses than a purely statistical survey.
The truth probably lies between the two and it is probably best to try and synergize the two approaches.
Whilst it will not answer a question completely, it will give some indications and allow further elaboration and hypothesis creation on a subject.
The case study research design is also useful for testing whether scientific theories and models actually work in the real world.
It is valid to conduct case studies but they should be tied in with more general statistical processes.
For example, a statistical survey might show how much time people spend talking on mobile phones, but it is case studies of a narrow group that will determine why this is so.