"What is the best way to develop marketing strategy?"
Developing any strategy begins by building a solid foundation. Understand the goal of marketing lies in achieving scalable growth when executed properly with the proper intent. The challenge companies face remains how to execute marketing properly.
1) Understand that you are building a system. A system that effectively generates x amount of revenue for y amount of investment. We know that x needs to be bigger than y consistently. Begin by focusing on a predictable way to execute this.
2) Know the company values you choose to stand for. This will influence the communications you generate across all your marketing efforts including your web copy.
3) Understand the problem you solve. This provides insight in terms of who the solution is most relevant for.
4) Define specifically who your solution is relevant for (known as buyer persona). The type of company, company size, the title of the person interested in the solution, how the solution improves what they are responsible for, how they are compensated and more.
5) Derive the value proposition from the buyer persona. Explain why your solution makes sense to them.
6) Elaborate on the talking points that support the value proposition.
7) Determine where to find the buyer persona. This includes which social platforms, how they research decisions they need to make, etc.
8) You can start by either engaging them directly with the intent to optimize your communication or marketing on those identified platforms.
9) Define your KPIs (key performance indicators) you will use to measure behaviors as it relates to your communication. The intent is to gain insight into how your communication facilitates a prospect along the buyer's journey.
10) Pivot. As data comes in, make changes to gauge results to optimize your investment.
As you are doing all these steps, I would keep in mind that marketing efforts compliment each other (paid, social, SEO, etc). Aligning your communication consistently across all the means you communicate remains the most effective method to optimize your spend.