Making those decisions is not an easy task, and unfortunately strict guidelines cannot be given because acceptable answers are highly dependent on the exact
nature, background, goals, and context of the study. To give you some direction, it might help to have a look at how these questions have been dealt with in
high-quality studies in your domain (which are generally published in peer-reviewed, high-impact journals). Because of the importance and difficulty of finding correct operationalizations of these issues, it is generally advisable to conduct a pilot study to test your data collection and analysis procedures.