I'm currently focusing on the Create Work Breakdown Structure process in the PMBOK Guide Scope Management Knowledge Area.
Louis Alderman (in the audio recordings for Velociteach's PMP examination preparation textbook, Sixth edition) notes the importance of the WBS: employing a WBS is the number one way for a PM to improve his/her project management practices.
How to build the WBS? In my job, I currently do a lot of task management work using the Smartsheet tool. Smartsheet has the advantage of being employed as a tool across multiple units in my organization. But I'm skeptical of Smartsheet's support for building graphical presentations, including the WBS chart. There are likewise limits to Microsoft Excel. As a result, I'm using the Cacoo online diagram and flowchart software.
Cacoo has templates for WBS charts (like the section of a WBS shown below. Note that I added numbering manually - it isn't included on the template.
Beyond WBS charts, Cacoo has templates for other project management needs, including fishbone diagrams, and Gantt charts.