For more details on the practice of writing field notes I recommend Emerson et al. Writing Ethnographic Fieldnotes (1995) University of Chicago Press.

Also, an experimental online project based on observations of public transport on the number 73 bus in London.

American Association for Public Opinion Research (AAPOR) – report on challenges of phone surveys in an era of mobile phones

Counting people: Census sensitivity (the Economist) – “numbers mean power, which is why counting people is so controversial”

Also highly recommended: Small, Mario Luis (2009). ‘How Many Cases Do I Need?’ On Science and the Logic of Case Selection in Field-Based Research. Ethnography 10(1): 5-38. [doi: 10.1177/1466138108099586] abstract excerpt: Today, ethnographers and qualitative researchers in fields such as urban poverty, immigration, and social inequality face an environment in which their work will be read, cited, and assessed by demographers, quantitative sociologists, and even economists….. Many have responded by incorporating elements of quantitative methods into their designs, such as selecting respondents ‘at random’ for small, in-depth interview projects or identifying ‘representative’ neighborhoods for ethnographic case studies, aiming to increase generalizability. This article assesses these strategies and argues that they fall short of their objectives