Take them individually, because each has a test.

Who your customer is means you can describe them specifically enough that somebody could repeat it to a third party. Not small businesses, which describes everybody, but a recognisable situation. If your description would fit most of your competitors, you have a category rather than a customer, and every marketing decision downstream of it will be harder than it needs to be.

What you charge means a considered number rather than one set in month two by somebody nervous about saying it aloud. The test is whether you have ever lost a customer on price. If not, you are probably still under, because a price nobody refuses sits below the point where anybody has to decide.

Which work is profitable means gross margin by type of work, not overall revenue. Nearly every business discovers that one category subsidises another and that the busiest work is not the best work. This is invisible without tracking what things actually cost you in time, which is why the tracking matters even when you bill by project.

Where customers come from means a written record, collected as they arrive, because it cannot be reconstructed later and it will disagree with your analytics. Six months of that column is the most valuable marketing information a first year business can own.

What does not indicate a successful year is being busy, which frequently conceals the opposite, or a strong final quarter, which may be seasonality. And a year that produced modest revenue while answering all four questions is a considerably better position than a stronger year that answered none, because the first is repeatable.

Add a fifth thing worth having, which is a written record of the decisions you made and why. Prices, positioning, which tools you chose, which work you turned down. In year two you will revisit several of them, and the reasoning matters more than the conclusion because circumstances change and you need to know which assumption a decision rested on.

Judge the year against what you have learned rather than against what you projected, because the projection was made by somebody who knew considerably less than you do now. Almost every first year plan is wrong in its specifics, and treating the gap as failure rather than as information is how owners talk themselves out of businesses that were working.