Strategic planning is many things but I like to think it's about moving teams on two axis that represent the strategy + planning parts.
1. Pessimist --> Optimist
This is the strategy part.
You'll have to convince people that the new destination is a better place.
Describe where the team needs to go by inspiring, influencing, nudging, etc. By using any means (data, qualitative and quantitative research, metaphors, legends, stories, testimonials, insights, case studies), you must clarify the sandbox. You don't want the sandbox to feel small – it can feel bigger than it was perceived before. You open up possibilities and you define what success looks like. You'll need to work a lot so everyone « can see it ».
2. Unpractical --> Practical
This is the planning part.
You'll have to convince people that you have enough gas to get there.
Describe how the team can get there by researching, mapping, detailing tactics, etc. You want the thing to feel as practical as possible. So if you decided that the team should develop a new product, open a store in a new market, cut half of its team, invest in augmented reality or change the packaging that's been there for 100 years, it must feel tangible. It might include a roadmap, key steps to get there, key people to include, case studies, etc. Ideally, it would include a simulation of the scenario or a minimum viable product. Break the thing into all the parts necessary and add details to each part. You'll need to work a lot so everyone « can own it ».