Every organisation has different objectives, therefore, there isn't one, single copy-paste recipe for effective communication strategy.
Creating one isn't a scientific project. I would compare it to an artwork and there are various ways in approach.
The more research you do, before drafting the plan for your brand, the better and there are no shortcuts here. The average time required for such research is around 3/4 of the overall time you may need to spend on the work itself.
If you are looking for guidance where to start, please consider the following:
1. Create your organisation communication objectives / statement of purpose
2. Gather all available business data for the purpose of assessment
3. Assess your current situation
4. Identify audience for the purpose of the work
5. Create message
6. Select tools & activities / methods
7. Draw timescale / action plan
8. Evaluating & conclusions
If you are considering hiring professionals or need some inspiration with support for your communications strategy project or perhaps you would rather not want to dip a toe in the matter, get in touch.