The goal of reviewing your territory and tiering your accounts (customers AND prospects) is to enable you to prioritize your time and proactively work on the right customers with the right amount of effort. When your accounts are ranked effectively, you can work on a cadence that helps you grow your opportunity pipeline by spending the right amount of time depending on the potential and current value of the customer/prospect.
To get started, you'll need to understand how the territory looks.
Remember, keep it simple and iterate!
Once you've organized your accounts and understand your routes to market, you can determine which resources to engage with to begin Account Planning.