The manner in which you organize your questions is a key tool that you can use to engage the respondent and ultimately improve your response rate.
My overall recommendation is that your questionnaire should have a logical and coherent flow. Think of a questionnaire as a type of conversation. A conversation will typically move from one topic to another in a logical fashion. A conversation that jumps around from one topic to another in a random fashion can be exhausting.
A conversation will also move from the general to the more specific. Therefore I suggest putting your general and non-threatening questions up front. This will serve to draw respondents into the survey.
There is a school of thought that argues that it is important to put the critical questions at the beginning of the survey. The premise is that if the respondent decides to quit partway through you still have obtained key information. I think it is preferable to maintain the integrity of the whole questionnaire and stick to the overall structure i.e. moving from the general to the specific.
One also sees a number ofquestionnaires that begin with demographic questions. I prefer to leave these questions to the end of the survey. My feeling is that they can be somewhat intrusive at the beginning.
To learn more about survey design, download our "7 Tips For Creating Successful Online Surveys".