"Every item in your database has a source and you will do yourself a great favor if you record that source when you enter that item, either electronically or in another medium. I can state from dreadful experience that you will come to regret it if you don't," declares Richard Pence in his article, Understanding Sources, Citations, Documentation And Evaluating Evidence In Genealogy.
Years will pass by before you know it, and your memory won't always be this sharp. I already have a small pile of clues that I cannot remember where I got them. Don't let this happen to you; always write down where and when you found the information. Unless it is an original document, I now write the source on the back of the copy.
It's a point most genealogists overlook, some knowingly. John Wylie adds, "Most of us must also admit that we've occasionally neglected to [cite something] and had to backtrack — time and effort we'd rather have spent seeking new information," in his article, How to Cite Sources.
Just because you record the source, doesn't always mean the information contained on a particular document is accurate. You may think that because the document came from a government office that it is correct. Think again!
Mary Grant said, "I soon realized that you couldn't just assume that other peoples research was correct. I found out that in order to be totally sure, you must do the research yourself, or else carefully study the other persons documentation, if given," on his web page, A Note about Sources.
Before you quickly write down the names of your latest ancestor, make sure you have a second source to verify the information.
Citing Your Sources
From the Board for Certification of Genealogists
Cite Your Sources : A Manual for Documenting Family Histories and Genealogical Records
A book by Richard S. Lackey
Evidence! : Citation & Analysis for the Family Historian
A book by Elizabeth Shown Mills