I want to combine many representative surveys in my analysis. What should I know? This is, unfortunately, something I was never exposed to as an undergraduate or in my PhD core (economics).
As an example, suppose I'm looking at three well-known nationally representative surveys: recent estimates from the American Communities Survey (ACS), the General Social Survey (GSS), and the NLSY79. Suppose each has an aggregate variable I'd like to use in an analysis of income, and further suppose each of the three independent variables are unique to their respective surveys.
I suppose cross-sectional analysis is out, since I'm dealing with different respondents. It also seems like doing a time-series analysis would be tricky if the surveys were administered at different times (the examples are). 
In short, what can I do, if anything, to observe interesting patterns in the data? What's kosher, and what's faux pas with regard to using results from different surveys?
 A: what can I do, if anything, to observe interesting patterns in the data?
Generate hypotheses and areas of interest by talking with other economists, policy makers, subject matter experts, whoever you think your audience is. As you form these ideas, attempt to confirm or disprove hypotheses. Don't create too many abstractions at first (variables aggregated from multiple variables, simplifications of variables, etc.) because you are still exploring. As you investigate your ideas and hypotheses, you may come up with some new ideas. 
what's faux pas with regard to using results from different surveys?
Combining data from multiple surveys is very risky unless the surveys were actually designed to be combined, as in wave surveys. There needs to be a good reason to combine the data. Faux pas:


*

*Combining surveys with incompatible sampling procedures

*Ignoring the potential effects of different field times, different survey formats, etc.

*Combining data from questions that were framed differently, had different responses available, etc.

