From the moment you start searching for information it is important to
have a method to track the sources and information you find.
If you don't you will probably find that you look in the same sources
more than once. It happened to me repeatedly when I first got started. I
was searching so many different places, but many of them sent me to the
same primary source.
A research log is a form that will be specific for one person, and you
will write every source you look at for a particular person. Write the
library call number or microfilm reel number. Write the name of a book,
the location, etc.
You think you will remember what we looked at, but as we get deeper and
deeper into a project, it becomes hard to remember all the sources.
Always carry your research logs with you, even if you think you are only
going to just research on one person. It seems like inevitably, you
find information about other relatives - and you need a place to record
that information.
Another option that someone suggested was to write a person's info on
the front of an index card, and tuck it in your pocket to take with
you. Record all sources searched on the back of the card.

This
sounded like a great idea, so I tried to get creative and use all pink
cards for ancestors on my mom's side, and all blue for those on my dad's
side.
I found them too small to record everything I needed, and they were too
easy to lose so it was back to the Research Log. Be sure to make many
copies of the log so that you have one for each person you will be
searching for information.