Don't leave a booby trap for another person. Make sure that all containers are appropriately labeled. OSHA's hazard communication standard and lab standards require labeling of containers.
As the containers get smaller, this requires some practice and creativity to provide sufficient information. Color coding, signal words, and flag label can be helpful.
Develop the habit of preparing the label and then filling the container.
Remove chemical label from empty containers before relabeling or discarding to avoid confusion about the contents.
When a new chemical is received, mark the date received, the full level, the initials of the individual who will be the “steward” for that container, and the date opened. The steward needs to be the one who wanted to order the chemical and is now most knowledgeable about the safe use, storage, and disposal of the chemical.
Source: Kaufman, James A., Laboratory Safety Guidelines - Expanded Edition, The Laboratory Safety Institute, www.labsafetyinstitute.org