Sometimes you can search on the web for actual surveys. However, some questionnaires or surveys are published within an article. To find them, do an article search in a database (examples: Business Source Premier, PsycINFO for psychology, SocINDEX for sociology, ERIC for education) on the topic of interest and add in the keywords survey* or questionnaire*.
In some cases, the actual questionnaire or survey is not published with the article, but is referred to within the text. In this case, look at the bibliography and find the reference to the questionnaire/survey itself, or to the original article where the questionnaire or survey was published. From that information, you should be able to track it down.
Some survey instruments are not free, and need to be purchased from the developer.