It's easily overlooked in the excitement of discovering another delicious snippet of information about an elusive ancestor, but every genealogist has to get into the habit of recording their sources.
We've all done it -- assured ourselves that the information is so staggeringly memorable that we'll remember forever exactly where and when we discovered it. Truth is, though, that while the new information may be indelibly etched on your brain, its source will very likely fade in a surprisingly short period of time.
Give yourself a break! You cannot expect yourself to remember the source of every single piece of genealogical data you come across. You simply need to record it, not least so that you can consider its weight when dealing with conflicting information.
It is not just you who benefits from this practice. It helps anyone else who wants to rely on your research to find the source document. There are a heck of a lot of genealogies now flying around either in cyberspace or in printed format. Some are well-researched. Many are not. The only way you or any other researcher can check the validity of another person's work is if sources have been cited.
Citing your sources is an excellent habit to acquire. There are some industry standards for doing this, but they are not really essential. Just make sure your citation provides enough information for another researcher to find your source.
Let 2011 be the year that citing your sources becomes an automatic response to new discoveries.