The Classification Tree should be focused on the CONTENT of the interactions you have with your stakeholders. If you find yourself wanting to put information about the Stakeholder or the Method of communication in your Classification Tree, we'd like to remind you that there are better fields for this type of data, namely Contact Groups and Communication Method.
A good Classification Tree ideally has about 15-20 top level categories, and no more than three levels of sub-categories. The reason for this is all about useability. There is a limit to which people are willing to scroll. Reading a long list of categories takes longer and leads to more people assigning it to the closest available category, rather than the best category for that item.
A good Classification Tree is easy to understand. Each of the main categories is distinct (the user should not have to look in multiple areas to find the suitable category). The terminology is clear. Make sure you use the definition field for each category - as the definition will show when the user hovers their mouse on the category name.
Ideally try and have a mix of 'issue' level categories and 'strategic' categories. You may only have one or two 'strategic' categories, but often they are the ones that give you the most useful information in your reporting. Look at your KPIs, evaluation criteria or organisation strategic goals to identify suitable 'strategic' categories for your tree.