Mixed methods are nice. Sometimes. But not always. They may even be utterly inappropriate. What is your question in the first place? Which type of data / info do you handle? Please provide some info on that...
Andres Santana put the right question -- the matter is not the method by the data you use (intend to use). You can check the data obtained through observations, survey or interviews by the data from corporate reports, managerial accounting or industry (analysts') reports and vice versa regardless of the method(s) you are applying to the data.
Hi Tulsi. If you gave the research question, it would be easier to suggest what triangulation would be the best. For each question, research area, or group of respondents, there may be different triangulation. This is how I see it.
The editors of the Journal of Mixed Methods (Fetters and Molina-Azorin) have recently recommended that we cease using the term triangulation because it has accumulated so many different meanings over the years. Are you pursuing the original meaning of the term, which was to assess whether qualitative and quantitative methods produced the same results?