Marc Bless has a great post about his personal scrum board evolving into a personal kanban. His personal retrospectives showed him a need to limit WIP, so he created a special section for WIP, while not losing track of his tasks awaiting the actions of others.Marc Says:

After a while I recognized the repeating problem of too many thing in progress. After a short personal retrospective I decided to improve my focus on the "in progress" lane. It seemed obvious to limit the number of things to work on in parallel. I splitted the "in progress" lane in two parts:a) an "on hold / wait" part for all the things that have been started but need external helpb) a "working on" part with focus on all the things in progress. This part now is a Kanban box with a limit of two tasks.