A good place to start with SEO planning is to understand where your website is right now and where you want to take it. It is useful to break things down from the top down to understand the work required to achieve your outcome goals.
An SEO strategy should be based on outcome goals or at the very least performance goals, traffic volume, rankings of groups of particular keywords, improve conversion rate from 1.5 to 3% etc.
The following diagram shows how processes and tasks are formed from working backward from your end goals, performance goals are set in a time frame which then determines the process and tasks required in order to hit the performance goals.
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