Below are some common things you want to see on kanban cards and some suggestions about how to visualize them.
Type of task
If your team works on varied types of work, use different colors for the cards based on the type of work it is so that it is easy to differentiate at a glance.
Have laminated small avatars or pictures for each person. Attach the avatars to cards to denote assignee.
Extra credit: On physical boards, match the number of available avatars per person to their individual WIP and ensure you don’t surpass the WIP limit for a particular person, if applicable.
Put a dot on the card for each day, starting with the day it is started (enters the first active column on your kanban board).
Extra credit: To get even more detail, choose a different color for the dots to differentiate different parts of the value stream. Example: Red for development, Blue for QA, Green for deployment, etc.
Mark the card in a consistent way to denote that it is “stuck.” You will also want to note how long it was stuck. This information will come in handy in defining problematic trends that lengthen cycle time. Many electronic boards have built in functions for this. On physical boards, perhaps put a red sticky on the card for a temporary tracking of blocked status. Again, dots can be your friend. You can put a dot in a particular color or area on the card for each day it is blocked.
Footnote: I prefer not to move work out of a workflow state when it is blocked. If you move things to an “On Hold” state or similar often you could be hiding a potential problem.
There are many more things you may choose to add to your cards or even niftier ways to visualize standard things. Share your ideas below!