Natural planning
Do you mean general, universal principles, or principles specific to one project?
Here are a few examples and the appropriate location for each:
1) "Arrive early to all meetings and appointments" or "maintain regular communication between others on my team and me". These are more general, universal principles that will likely apply to several projects. I would create an Area of Focus, perhaps called "Personal Principles" and create a document that you can refer to when it is time to ask "how am I doing on these?" In that document I would include principles that you want to apply to several projects, or to life in general.
Note that if you are trying to create a habit, then you may temporarily have a project of maintaining punctuality for some period of time.
2) "All grammar, syntax, spelling, and punctuation doublechecked." This principle may be one of the guidelines that is especially important for one project (e.g. writing a published article) but may not apply to all projects.
Principles for a particular project would fit onto your Project Plan, in accordance with the Natural Planning Model.
Hope these help!
JV474