A communication plan answers one question: who needs what information, when, and through which channel? Without one, you default to 'send everything to everyone' - which means the people who need critical updates drown in noise, and the people who don't need anything learn to ignore you entirely.
What goes in a communication plan
For each stakeholder group, define: what information they need, how often they need it, what format works best for them, who's responsible for delivering it, and how they can escalate if they need more. A steering committee member needs a one-page dashboard weekly. The project team needs a 15-minute standup daily. The wider organisation needs a monthly newsletter that doesn't assume they know what a sprint is.
The most common mistake is designing the plan around what's easy for the PM to produce rather than what's useful for the stakeholder to receive. A detailed 10-page status report is easy for you (you're already tracking the data), but it's useless to an executive who wants three bullet points and a RAG status. Flip it: ask stakeholders what they want, then design the plan around that. Yes, it's more work. Yes, it means your updates actually get read.
Include a 'how to escalate' section in the plan. A stakeholder who needs information urgently should know exactly who to contact and how. Without this, they'll escalate through whatever channel is available - usually by emailing your boss, copying your boss's boss, and adding a subject line that makes everyone's day worse.
Channel discipline (or: please stop sending everything by email)
Every channel has a strength. Email is good for records and async communication. Slack is good for quick questions and informal updates. Meetings are good for decisions and alignment. A shared document is good for collaboration and version control. The problem is not having too many channels - it's using them all for everything until nobody knows where to look for anything.
Set explicit rules. 'All status updates go in the project tracker, not email. All decisions are captured in the decision log, not Slack threads over three days. All document changes happen in the shared drive, not on local copies named final_v2_REVIEWED.docx.' The team will forget these rules. That's fine - gently redirect them until the habit forms. A project where everyone knows where to find information runs noticeably smoother than one where finding yesterday's decision requires an archaeological dig through your chat history.
The single most effective communication habit: the weekly one-page status report. Not a dashboard with 47 metrics. Not a deck with 12 slides. One page: what we accomplished, what's blocked, what's next, and the RAG status. Send it the same day every week. Stakeholders will learn to expect it, read it, and trust it. That consistency is worth more than any amount of detailed reporting you could produce on demand.
Summary & next steps
A communication plan defines who gets what information, when, and how. Design it around stakeholder needs, not your convenience. Establish channel discipline - each channel has a purpose, use it accordingly. The weekly one-page status report is the single highest-ROI communication habit you can build.
Next: managing resistance - because not every stakeholder is rooting for you, and that's fine if you know how to handle it.