In the 1950's TV show, Dragnet, one of Sgt. Joe Friday's catchphrases was "We just want the facts, Ma'am." Most beginning genealogists assume that is all they are searching for - just the facts. But as most any "seasoned" family history researcher will tell you, sometimes writing down more than "just the facts" can be the key to breaking through a brick wall later.
When I first started reaching out past the recollection of my living relatives and into letters, Census data and other records, I made a habit of keeping two notepads with me. One, I used to record the facts that I found in a particular record and the citation for the records - good genealogical research information. The other pad was my "Thoughts" pad. I used this notepad to record my on-the-fly thoughts about the record I was working with. Most of the time, the notes were a simple connect the dots such as "Record confirms birth date for Great Grandpa Link." Every so often, I would jot down what I call a "huh?" note. Those are the notes about things that just don't make sense, don't quite seem to fit, or they fit but open up other questions.
Many times, you will find that those hunches and assumptions that you write down on the fly prove to be correct once enough proof has been acquired. Perhaps more importantly, the questions that you write down while you are recording the facts will often lead you down another avenue of research that yields unexpected and very valuable results. Never assume that all you want from a document is "just the facts." Keep track of your thoughts and questions about documents because you never know when those random thoughts and questions may just end up helping you break through that impenetrable brick wall.