From the FamilySearch Research Wiki:
One of the most fundamental and important principles of family history research is to organize and document AS YOU GO! Good documentation includes:
- Research logs—Fill in the purpose of each search, and source data on logs before looking at the source. After success, list where you found the copy. Log strategies.
- Family group records—Keep up-to-date with source footnotes for every event. Add all events like census, military service, and migrations to the family group record.
- Photocopies of most sources—If the repository will allow it, ALWAYS make a photocopy.
- Well-organized files—Stay organized by completing paperwork and filing before starting another search.
Follow the link above for more details on how documentation supports your research effort.