In the order of effectiveness of general communication: Face-to-face > Phone call > Email.
Complex Ideas: Layout idea in a PowerPoint/Word/Excel Document, communicate through email and follow up with Face-to-face or Phone call presentation.
If the points discussed and decisions taken are important, follow up after the meeting with a meeting minutes to have everything recorded in black-and-white. If the details discussed are not so important, or if their is already a strong drive for proper controls being included in the project, then do not sweat the small details (no need to capture in black-and-white, and spend the time on more important tasks).
Capture all the IT Security and Risk related discussion and decision points for a project in one single document for central tracking.
Always ensure that written communication is “toned down” and is highlighting the best of intentions. Any conflict should be resolved through a face-to-face meeting or through a phone conversation.