A sale is usually the largest single financial event in an owner's life and the one they have least practice at. The other side of the table does this for a living. This list is chosen to narrow that gap.
Two threads run through it. The first is value: what a buyer is actually paying for, which is rarely what the seller thinks, and why a business that cannot run without you is worth measurably less. The second is negotiation and process, because much of the final number is decided by how the deal is structured rather than by the headline figure.
Read it two or three years before you intend to sell, not two months. Almost everything that raises the price takes that long to put in place, and none of it can be done during a due diligence process.