A WIP limit really depends on the team and what you are trying to accomplish. WIP Limits can encourage team work, expose bottlenecks and reduce multitasking.
To encourage team work, drop the WIP limit lower than the number of people on the team. For a team of six developers, a WIP limit of three would mean that every developer was pairing up to work on a story. If you wanted to try out mob programming you’d drop your WIP limit to one. If you want each developer to work one thing as individual then set your WIP limit to the total number of people on the team.
To expose bottlenecks in a specific column, drop your WIP limits on that column. That will force the team to swarm on the problems that are causing the back up.
To limit task switching reduce the WIP limit. If the WIP limit is less than or equal to the number of developers on the team, then developers shouldn’t be working on more than one thing at a time.
For more information on WIP Limits: http://kanbanblog.com/article/cracking-the-wip.html http://blog.kanbanize.com/kanban-101-applying-wip-limits/ https://www.crisp.se/gratis-material-och-guider/kanban