The exercise is simple and uncomfortable. List every step, every place they encounter you, and every action required of them. For a service business that typically runs from a search, to your site, to a form, to your reply, to a conversation, to a proposal, to a decision, to the work, to an invoice, to whatever happens afterward. Then walk it yourself, as a stranger would, and note where you had to wait, where something was unclear, and where you had to do something you would rather not.
What the exercise reveals is usually not a marketing problem. It is that your reply takes two days, that the proposal asks somebody to print and sign something, that there is a four day silence between agreement and starting where the customer wonders whether anything is happening, or that after the work is finished you never contact them again. Those gaps are where customers are lost and they are invisible from inside the business because you experience the process as a series of tasks rather than as a waiting experience.
Pay particular attention to the transitions rather than the steps. Handovers between channels, between people, and between stages are where things drop, and they are where a customer feels the seams. The most common one in a small business is between somebody expressing interest and somebody actually being contacted, and it is frequently measured in days when it could be measured in hours.
Include what happens after the sale, which is the half most maps omit. Onboarding, delivery, the invoice, the follow up, and the point at which somebody would buy again. For a business that depends on repeat custom or referral, that section produces more improvement than anything before the sale.
Do it on one page rather than as a project. A hand drawn sequence with the friction points marked is more useful than a formal document, because the purpose is to identify three things to fix rather than to produce an artefact. Redo it annually, because the process drifts as the business changes and nobody notices.