Creswell's book on 5 approaches to qualitative research is one of our all time go to books. It is easy to read for any level of researcher, and it provides new insights the more times you read it. The tables presenting comparisons between approaches are particularly useful. These allow you to not only argue and justify your approach/es, but to also justify why you did not make other certain decisions. For instance, using the table to argue the number of interviews you did for an ethnography, can help you to argue why you did not do more or less interviews - an approach more suited to another method such as a case study, or a narrative study.
We often fail as researchers to consider the pros and cons of each of the available approaches, and we choose the ones we think will yield the "best" results, or will be the most fun to do. Without considering the technical advantages and disadvantages of each approach means we are not doing justice to our research and participants because we have not fully considered the scope of our work. We encourage you to map our your own approaches with your justifications for your choices, and use these to present your decisions to your supervisors and colleagues.