There are a number of ethical considerations to be aware of before conducting your research. For instance, individuals participating in surveys and experiments must do so voluntarily and in full awareness of what they are getting into, with suitable guarantees of confidentiality or even anonymity. While ethical issues are generally less salient when conducting qualitative research using unobtrusive measures (like a document analysis), it is always important to be aware of these issues. You can find further guidelines in Dutch here.
It is also important to maintain high ethical standards when reporting your research. Key issues here include accurate reporting, avoiding plagiarism, and proper acknowledgment of the work you draw on. Guidelines on this can be found here.
Babbie, Earl (2004). The Practice of Social Research (12th edition). Belmont: Wadsworth/Thomson. Chapter 3.
Shadish, William R., Thomas D. Cook and Donald T. Cambell (2002). Experimental and Quasi-Experimental Designs for Generalized Causal Inference. Boston: Houghton Mifflin. Chapter 9.
De Vaus, David (2001). Research Design in Social Research. London: Sage. Chapters 5, 8, 11, 14.