This is a huge question, and my answer in a nutshell, is that you should not attempt to remain ‘unbiased’.
I’ll try to approach your question via the work of Alfred Schutz, a sociologist from the mid-20th century. He argued that, unlike the objects of study in the natural sciences, those studied in social research are active, sense-making human beings, who are engaged in interpreting and ascribing meaning to their world in interaction with each other. Yet this also applies to the social scientist herself, who is a further active interpreter of the same social world inhabited by those she would observe and understand.
A consequence for social science is that researchers need to acknowledge their own interpretative work as they analyse the social worlds they are researching, and recognise that in making sense of an actor’s sense-making, they themselves impose a second level of interpretation, that is itself subject to wht Weber called verstehen (understanding). This is a critical issue for social researchers, especially those using qualitative interpretivist approaches, as they must recognise that their human, rationalising, constructive activity is behind their analyses of actors’ life-worlds.
This analysis has a number of consequences. First, it acknowledges that people are engaged in an on-going project of producing the social world, and therefore that their sense-making must itself become part of the subject-matter of a social science, ruling out a simplistic limitation of study to ‘social facts’, and accepting the context-specificity of knowledge.
Second, it recognises that the tools of study in social science are human beings’ own capacities as interpreters of the world. As such, these instruments work by means of exactly the same processes of intersubjective meaning-attribution that the social scientist seeks to study. While there may be an aspiration to objectivity by the social scientist, this inheres only in her detachment from the practical commitments and interests of her subjects, not from some essential difference in her ability to interpret free from values, norms and so forth.
This leads to the third feature, the need for social scientists to be reflexive about their interpretative work, both to aspire to detachment but at the same time to accept its ultimate impossibility.
This ‘post-positivist’ analysis has led to two contrary perspectives on doing qualitative research, which can be broadly described as realist and constructivist. The former adheres to the notion that there is some objective reality to the social world, while acknowledging that the Schutzian analysis of social science as interpretative and therefore ultimately subjective sense-making, precludes the discovery of that reality once-and-for-all. All that can be achieved is the aspiration to knowledge through rigour, multiple data analysis and theory-building and testing. Constructivists, by contrast, consider not only that objective knowledge is impossible because of these problems of interpretation, but also that – given that the world is variously constructed by human beings with their context- and interest-specific views of the world anyway -- that reality is itself multiple, contingent and value-laden.
What follows is that, rather than trying to avoid bias, you need to acknowledge it, and if anything, use your reflexivity as a human being to add to the richness of the account you offer when you report the qualitative data you have collected and analysed.
Is that of any help?