Try these options:
Involve the people who’ll be doing the work. When possible, involve them during the initial development of the WBS. If they join the project after the initial planning, have them review and critique the WBS before they begin work.
Review and include information from WBSs from similar projects. Review plans and consult people who’ve worked on projects similar to yours that were successful. Incorporate your findings into your WBS.
Keep your WBS current. When you add, delete, or change WBS elements during your project, be sure to reflect these changes in your WBS.
Make assumptions regarding uncertain activities. If you’re not sure whether you’ll do a particular activity, make an assumption and prepare your WBS based on that assumption. Be sure to document that assumption. If your assumption proves to be wrong during the project, change your plan to reflect the true situation.
Remember that your WBS identifies only your project’s deliverables; it doesn’t depict their chronological order. Nothing is wrong with including activities from left to right or top to bottom in the approximate order that you’ll perform them. However, in complex projects, you may have difficulty showing detailed interrelationships among activities in the WBS format. The purpose of the WBS is to ensure that you identify all project deliverables.