Give yourself enough time to locate and interpret the primary sources
you need for your research.
Using primary sources can be more time consuming. You will also be limited by what is available online or in published form, and how far you are willing to travel.
Understand the historical context of the documents you are using (point of view, language usage, bias)
Consult secondary sources as needed to help you evaluate your primary sources. Also, use appropriate historical language when searching for archival materials.
Evaluate the format
If using a primary source surrogate, be sure that it is from a credible site and consider if the format has affected the integrity of the original source.